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VCA822
SBOS343D – SEPTEMBER 2007 – REVISED OCTOBER 2015
VCA822 Wideband, > 40-dB Gain Adjust Range, Linear in V/V
Variable Gain Amplifier
1 Features
3 Description
•
The VCA822 device is a DC-coupled, wideband,
linear in V/V, continuously variable, voltage-controlled
gain amplifier. It provides a differential input to singleended conversion with a high-impedance gain control
input used to vary the gain down 40dB from the
nominal maximum gain set by the gain resistor (RG)
and feedback resistor (RF).
1
•
•
•
•
•
•
150-MHz Small-Signal Bandwidth
(G = +10 V/V)
137 MHz, 5 VPP Bandwidth (G = +10 V/V)
0.1-dB Gain Flatness to 28 MHz
1700 V/μs Slew Rate
> 40-dB Gain Adjust Range
High Gain Accuracy: 20 dB ±0.3 dB
High Output Current: ±160 mA
The internal architecture of the VCA822 device
consists of two input buffers and an output current
feedback amplifier stage integrated with a multiplier
core to provide a complete variable gain amplifier
(VGA) system that does not require external
buffering. The maximum gain is set externally with
two resistors, providing flexibility in designs. The
maximum gain is intended to be set between +2 V/V
and +100 V/V. Operating from ±5-V supplies, the gain
control voltage for the VCA822 device adjusts the
gain linearly in V/V as the control voltage varies from
+1 V to 1 V. For example, set for a maximum gain of
+10 V/V, the VCA822 device provides 10 V/V, at
1-V input, to 0.1 V/V at –1 V input of gain control
range. The VCA822 device offers excellent gain
linearity. For a 20-dB maximum gain and a gaincontrol input voltage varying between 0 V and 1 V,
the gain does not deviate by more than ±0.3 dB
(maximum at +25°C).
2 Applications
•
•
•
•
•
•
Differential Line Receivers
Differential Equalizers
Pulse Amplitude Compensation
Variable Attenuators
Voltage-Tunable Active Filters
Drop-In Upgrade to LMH6503
Device Information (1)
PART NUMBER
VCA822
(1)
Differential Equalizer
VIN1
RL
-VIN
0
VOUT
CL
RG-
RS
3
VCA822
C1
VIN2
Equalized Frequency
Response
6
FB
RG
3.00 mm × 3.00 mm
9
20W
Gain (dB)
R1
VSSOP (10)
Differential Equalization of an RC Load
RG+
RS
BODY SIZE (NOM)
8.65 mm × 3.91 mm
For more information, see Mechanical Packaging and
Orderable Information.
RF
+VIN
PACKAGE
SOIC (14)
-3
-6
Initial Frequency Response
of VCA822 with RC Load
-9
-12
-15
-18
-21
-24
RL = 75W
CF = 100pF
1M
10M
100M
1G
Frequency (Hz)
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
VCA822
SBOS343D – SEPTEMBER 2007 – REVISED OCTOBER 2015
www.ti.com
Table of Contents
1
2
3
4
5
6
7
Features ..................................................................
Applications ...........................................................
Description .............................................................
Revision History.....................................................
Device Comparison Table.....................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
2
4
4
5
7.1
7.2
7.3
7.4
7.5
7.6
7.7
Absolute Maximum Ratings ...................................... 5
ESD Ratings.............................................................. 5
Recommended Operating Conditions....................... 5
Thermal Information .................................................. 5
Electrical Characteristics: VS = ±5 V......................... 6
Typical Characteristics: VS = ±5 V, DC Parameters . 9
Typical Characteristics: VS = ±5 V, DC and PowerSupply Parameters .................................................. 10
7.8 Typical Characteristics: VS = ±5 V, AVMAX = +2
V/V ........................................................................... 11
7.9 Typical Characteristics: VS = ±5 V, AVMAX = +10
V/V ........................................................................... 14
7.10 Typical Characteristics: VS = ±5 V, AVMAX = +100
V/V ........................................................................... 18
8
Parameter Measurement Information ................ 21
9
Detailed Description ............................................ 22
9.1 Overview ................................................................. 22
9.2 Feature Description................................................. 22
9.3 Device Functional Modes........................................ 22
10 Application and Implementation........................ 25
10.1 Application Information.......................................... 25
10.2 Typical Applications .............................................. 27
10.3 System Examples ................................................. 34
11 Power Supply Recommendations ..................... 36
12 Layout................................................................... 36
12.1 Layout Guidelines ................................................. 36
12.2 Layout Example .................................................... 37
12.3 Thermal Considerations ........................................ 37
13 Device and Documentation Support ................. 38
13.1
13.2
13.3
13.4
13.5
Device Support......................................................
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
38
38
38
38
38
14 Mechanical, Packaging, and Orderable
Information ........................................................... 38
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision C (December 2008) to Revision D
•
Added Pin Configuration and Functions section, ESD Ratings table, Recommended Operating Conditions table,
Feature Description section, Device Functional Modes, Application and Implementation section, Power Supply
Recommendations section, Layout section, Device and Documentation Support section, and Mechanical,
Packaging, and Orderable Information section ..................................................................................................................... 1
Changes from Revision B (August 2008) to Revision C
•
Page
Revised second paragraph in the Wideband Variable Gain Amplifier Operation section describing pin 9.......................... 27
Changes from Revision A (October 2007) to Revision B
•
Page
Page
Changed storage temperature range rating in Absolute Maximum Ratings table from –40°C to +125°C to –65°C to
+125°C.................................................................................................................................................................................... 5
Changes from Original (September 2007) to Revision A
Page
•
Changed GMAX to AVMAX throughout document....................................................................................................................... 1
•
Changed G to AVMAX in conditions in the Electrical Characteristics: VS = ±5 V table............................................................. 6
•
Changed 5th row of AC Performance section in the Electrical Characteristics: VS = ±5 V table .......................................... 6
•
Changed 4th row of Output section in the Electrical Characteristics: VS = ±5 V table........................................................... 6
•
Changed Figure 7, the title of Figure 8, the title of Figure 9, the title of Figure 10, and Figure 11 in the ±5V, DC and
Power-Supply Parameters Typical Characteristics ............................................................................................................. 10
•
Changed Figure 78, Figure 18, Figure 20, Figure 22, and Figure 27 in the ±5V, AVMAX = +2V/V Typical
Characteristics ..................................................................................................................................................................... 11
2
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•
Changed Figure 32, Figure 48, and Figure 52 in the ±5V, AVMAX = +10V/V Typical Characteristics. .................................. 14
•
Changed Figure 53 and Figure 72 in the ±5 V, AVMAX = +100 V/V Typical Characteristics ................................................ 18
•
Changed Table 1 in the Demonstration Boards section....................................................................................................... 25
•
Changed 2200V/μs to 1700V/μs in first paragraph of the Wideband Variable Gain Amplifier Operation Application
section. ................................................................................................................................................................................. 27
•
Changed rail quantity for VCA822ID in the Ordering Information table .............................................................................. 38
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SBOS343D – SEPTEMBER 2007 – REVISED OCTOBER 2015
5
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Device Comparison Table
VCA822 Related Products
DUALS
GAIN ADJUST RANGE
(dB)
INPUT NOISE
(nV/√Hz)
SIGNAL BANDWIDTH (MHz)
VCA810
—
—
VCA2612
80
2.4
35
45
1.25
—
80
VCA2613
45
1
80
—
VCA2615
52
0.8
50
—
VCA2617
48
4.1
50
VCA820
—
40
8.2
150
VCA821
—
40
7.0
420
VCA822
—
40
8.2
150
VCA824
—
40
7.0
420
SINGLES
6 Pin Configuration and Functions
D Package
14-Pin SOIC
Top View
DGS Package
10-Pin VSSOP
Top View
+VCC
1
14 +VCC
VG
2
13 NC
+VIN
3
12 FB
+RG
4
11 GND
-RG
5
10 VOUT
-VIN
6
9
VREF
-VCC
7
8
-VCC
FB
1
10 GND
+VCC
2
9
VOUT
VG
3
8
-VCC
+VIN
4
7
-VIN
+RG
5
6
-RG
NC = No Connection
Pin Functions
PIN
NAME
SOIC
VSSOP
I/O
DESCRIPTION
FB
12
1
I
GND
11
10
—
Feedback Resistor Input
Ground
NC
13
—
—
No Connect
+RG
4
5
I
Gain Set Resistor
–RG
5
6
I
Gain Set Resistor
–VCC
7, 8
8
P
Negative Supply
+VCC
1, 14
2
P
Positive Supply
VG
2
3
I
Gain Control
–VIN
6
7
I
Inverting Input
+VIN
3
4
I
Noninverting Input
VOUT
10
9
O
Output
VREF
9
—
I
Output Voltage Reference
4
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SBOS343D – SEPTEMBER 2007 – REVISED OCTOBER 2015
7 Specifications
7.1 Absolute Maximum Ratings
Over operating free-air temperature range, unless otherwise noted. (1)
MIN
Power supply
Internal power dissipation
MAX
UNIT
±6.5
V
See Thermal Information
Input voltage
±VS
V
Lead temperature (soldering, 10 s)
260
°C
Junction temperature (TJ)
150
°C
Junction temperature (TJ), maximum continuous operation
140
°C
125
°C
Storage temperature
(1)
–65
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
7.2 ESD Ratings
VALUE
V(ESD)
(1)
(2)
Electrostatic discharge
Human-body model (HBM), per ANSI/ESDA/JEDEC JS-001 (1)
±2000
Charged-device model (CDM), per JEDEC specification JESD22-C101 (2)
±500
Machine model (MM)
±200
UNIT
V
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.
7.3 Recommended Operating Conditions
over operating free-air temperature range (unless otherwise noted)
Operating voltage
Operating temperature
MIN
NOM
MAX
7
10
12
UNIT
V
–40
25
85
°C
7.4 Thermal Information
VCA822
THERMAL METRIC
(1)
D [SOIC]
DGS [VSSOP]
14 PINS
10 PINS
UNIT
RθJA
Junction-to-ambient thermal resistance
90.3
173.1
°C/W
RθJC(top)
Junction-to-case (top) thermal resistance
49.8
46.6
°C/W
RθJB
Junction-to-board thermal resistance
44.9
94.3
°C/W
ψJT
Junction-to-top characterization parameter
13.8
2.2
°C/W
ψJB
Junction-to-board characterization parameter
44.6
92.7
°C/W
RθJC(bot)
Junction-to-case (bottom) thermal resistance
n/a
n/a
°C/W
(1)
For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report, SPRA953.
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7.5 Electrical Characteristics: VS = ±5 V
At AVMAX = +10 V/V, RF = 1 kΩ, RG = 200 Ω, and RL = 100 Ω, 25°C, unless otherwise noted.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
TEST
LEVEL (1)
AC PERFORMANCE
Small-signal bandwidth (SOIC-14
Package)
Large-signal bandwidth
Gain control bandwidth
Bandwidth for 0.1dB flatness
Slew rate
AVMAX = +2V/V, VO = 1 VPP, VG = 1 V
168
MHz
C
AVMAX = +10V/V, VO = 1 VPP, VG = 1 V
150
MHz
C
AVMAX = +100V/V, VO = 1 VPP, VG = 1 V
118
MHz
C
AVMAX = +10V/V, VO = 5VPP, VG = 1 V
137
MHz
C
MHz
B
MHz
C
V/μs
B
ns
B
ns
C
dBc
B
dBc
B
VG = 0VDC + 10 mVPP
25°C (2)
170
0°C to 70°C (3)
170
–40°C to +85°C (3)
165
AVMAX = +10V/V, VO = 1VPP, VG = 1 V
AVMAX = +10V/V, VO = 5-V Step, VG = 1
V
28
25°C (2)
1500
0°C to 70°C (3)
1500
–40°C to +85°C (3)
1450
25°C (2)
Rise-and-fall time
Settling time to 0.01%
Harmonic distortion, 2nd-harmonic
Harmonic distortion, 3rd-harmonic
AVMAX = +10V/V, VO = 5-V Step, VG = 1
V
VO = 2VPP, f = 20MHz, VG = 1 V
1700
2.5
3.1
0°C to 70°C (3)
3.2
–40°C to +85°C (3)
3.2
AVMAX = +10V/V, VO = 5V Step, VG = 1 V
VO = 2VPP, f = 20MHz, VG = 1 V
200
11
25°C (2)
–60
0°C to 70°C (3)
–60
–40°C to +85°C (3)
–60
25°C (2)
–66
0°C to 70°C (3)
–66
–40°C to +85°C (3)
–66
–62
–68
Input voltage noise
f > 100kHz, VG = 1 V
8.2
nV/√Hz
C
Input current noise
f > 100kHz, VG = 1 V
2.6
pA/√Hz
C
dB
A
dB
A
dB
A
dB
A
μA
A
nA/°C
B
kΩ || pF
C
mV
A
μV/°C
B
GAIN CONTROL
25°C (2)
Absolute gain error
AVMAX = +10V/V, VG = 1 V
AVMAX = +10V/V, 0 < VG < 1 V
±0.5
±0.6
AVMAX = +10V/V, –0.8 < VG < 1 V
Relative to maximum gain
–40°C to +85°C (3)
±0.37
Average gain control bias current drift
VG = 0 V
VG = 0 V
±1.06
±1.9
0°C to 70°C (3)
±2.1
–40°C to +85°C (3)
±2.2
–26
–24
0°C to 70°C (3)
–24
–40°C to +85°C (3)
–23
25°C (2)
Gain control bias current
±0.3
±0.34
25°C (2)
Gain at VG = –0.9V
±0.05
0°C to 70°C (3)
25°C (2)
Gain deviation
±0.4
–40°C to +85°C (3)
25°C (2)
Gain deviation
±0.1
0°C to 70°C (3)
22
30
0°C to 70°C (3)
35
–40°C to +85°C (3)
37
0°C to 70°C (3)
±100
–40°C to +85°C (3)
±100
Gain control input impedance
70 || 1
DC PERFORMANCE
25°C (2)
Input offset voltage
Average input offset voltage drift
(1)
(2)
(3)
6
AVMAX = +10V/V, VCM = 0 V, VG = 0 V
AVMAX = +10V/V, VCM = 0 V, VG = 0 V
0°C to 70°C (3)
±4
±17
±17.8
–40°C to +85°C (3)
±19
0°C to 70°C (3)
±30
–40°C to +85°C (3)
±30
Test levels: (A) 100% tested at 25°C. Over temperature limits set by characterization and simulation. (B) Limits set by characterization
and simulation. (C) Typical value only for information.
Junction temperature = ambient for +25°C tested specifications.
Junction temperature = ambient at low temperature limit; junction temperature = ambient +23°C at high temperature limit for over
temperature specifications.
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Electrical Characteristics: VS = ±5 V (continued)
At AVMAX = +10 V/V, RF = 1 kΩ, RG = 200 Ω, and RL = 100 Ω, 25°C, unless otherwise noted.
PARAMETER
TEST CONDITIONS
MIN
25°C (2)
Input bias current
Average input bias current drift
AVMAX = +10V/V, VCM = 0 V, VG = 0 V
AVMAX = +10V/V, VCM = 0 V, VG = 0 V
Average input offset current drift
AVMAX = +10V/V, VCM = 0 V, VG = 0 V
AVMAX = +10V/V, VCM = 0 V, VG = 0 V
MAX
Maximum current through gain
resistance
19
25
29
–40°C to +85°C (3)
31
0°C to 70°C (3)
±90
–40°C to +85°C (3)
±90
±0.5
±3.2
–40°C to +85°C (3)
±3.5
0°C to 70°C (3)
±16
–40°C to +85°C (3)
±16
±2.6
0°C to 70°C (3)
TEST
LEVEL (1)
μA
A
nA/°C
B
μA
A
nA/°C
B
mA
B
V
A
V
A
dB
A
±2.55
±2.55
–40°C to +85°C (3)
UNIT
±2.5
0°C to 70°C (3)
25°C (2)
IRG
MAX
0°C to 70°C (3)
25°C (2)
Input offset current
TYP
±2.5
INPUT
Most positive input voltage
RL = 100Ω
25°C (2)
+1.6
0°C to 70°C (3)
+1.6
–40°C to +85°C (3)
+1.6
25°C (2)
Most negative input voltage
Common-mode rejection ratio
RL = 100Ω
VCM = ±0.5V
+1.6
–2.1
–2.1
0°C to 70°C (3)
–2.1
–40°C to +85°C (3)
–2.1
25°C (2)
65
0°C to 70°C (3)
60
–40°C to +85°C (3)
60
80
Input impedance, differential
0.5 || 1
MΩ || pF
C
Input impedance, common-mode
0.5 || 2
MΩ || pF
C
V
A
V
A
mA
A
0.01
Ω
C
Specified operating voltage
±5
V
C
Minimum operating voltage
±3.5
V
C
V
A
mA
A
mA
A
dB
A
OUTPUT
25°C (2)
0°C to 70°C (3)
RL = 1kΩ
Output voltage swing
RL = 100Ω
Output current
Output impedance
VO = 0V, RL = 5Ω
±3.8
±4.0
±3.75
–40°C to +85°C (3)
±3.7
25°C (2)
±3.7
0°C to 70°C (3)
±3.6
–40°C to +85°C (3)
±3.5
25°C (2)
±140
0°C to 70°C (3)
±130
–40°C to +85°C (3)
±130
AVMAX = +10V/V, f > 100kHz, VG = 1V
±3.9
±160
POWER SUPPLY
25°C (2)
Maximum operating voltage
0°C to 70°C (3)
–40°C to +85°C (3)
25°C (2)
Maximum quiescent current
VG = 0V
36
0°C to 70°C (3)
–40°C to +85°C (3)
38
25°C (2)
Minimum quiescent current
VG = 0V
36
0°C to 70°C (3)
Power-supply rejection ratio
VG = +1V
34.5
34
–40°C to +85°C (3)
–PSRR
37
37.5
33.5
25°C (2)
–61
0°C to 70°C (3)
–59
–40°C to +85°C (3)
–58
–68
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Electrical Characteristics: VS = ±5 V (continued)
At AVMAX = +10 V/V, RF = 1 kΩ, RG = 200 Ω, and RL = 100 Ω, 25°C, unless otherwise noted.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
TEST
LEVEL (1)
THERMAL CHARACTERISTICS
Specified operating range, D package
θJA
8
Junction-to-ambient Thermal
resistance
–40 to +85
MSOP-10 (DGS)
SOIC-14 (D)
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°C
C
130
°C/W
C
80
°C/W
C
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7.6 Typical Characteristics: VS = ±5 V, DC Parameters
At TA = 25°C, RL = 100 Ω, VG = 1 V, and VIN = single-ended input on +VIN with –VIN at ground, unless otherwise noted.
40
IRG MAX = 2.6mA
VIN MAX(VPP) = 2 ´ RG ´ IRG MAX (AP)
Maximum Gain Adjust Range (dB)
Differential Input Voltage (VPP)
10
1
IRG = 2.6mA
AVMAX(V/V) = 2 ´ [RF/VIN(VPP)] ´ 2 ´ IRG (AP)
35
30
25
VO = 1VPP
20
VO = 2VPP
15
VO = 4VPP
10
VO = 3VPP
5
0
0.1
10
100
1k
100
1k
Gain Resistor (W)
Figure 1. Maximum Differential Input Voltage vs RG
Figure 2. Maximum Gain Adjust Range vs RF
IRG = 2.6mA
AVMAX(V/V) = 2 ´ [RF/VIN(VPP)] ´ 2 ´ IRG (AP)
50
RF = 3kW
40
RF = 4kW
Gain (V/V)
Maximum Gain Adjust Range (dB)
60
RF = 5kW
30
RF = 500W
20
RF = 1.5kW
RF = 2kW
0
0.1
21
1
0
-0.4
0.4
0.8
Figure 3. Maximum Gain Adjust Range vs
Peak-to-Peak Output Voltage
Figure 4. Gain Error Band vs
Gain Control Voltage
Gain (V/V)
Gain (V/V)
-0.8
Control Voltage (V)
18
Data
17
16
Relative Error to Linear Regression
15
Linear Regression
13
0
Relative Error to
Maximum Gain
Output Voltage (VPP)
19
14
Absolute Error
4
3
-1
-1.2
10
Data Equation:
y = 20log (4.9619x + 5.0169)
20
11
10
9
8
7
6
5
2
1
0
RF = 1kW
10
10k
Feedback Resistor (W)
0.2
0.4
0.6
0.8
1.0
24
22
20
18
16
14
12
10
8
6
4
2
0
-2
-4
-6
-0.8
1.2
Relative Error to Linear Regression
Linear Regression
Data Equation:
y = 20log (4.9619x + 5.0169)
Data
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
Control Voltage (V)
Control Voltage (V)
Figure 5. Gain Error Band vs
Gain Control Voltage
Figure 6. Gain Error Band vs
Gain Control Voltage
0.8
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7.7 Typical Characteristics: VS = ±5 V, DC and Power-Supply Parameters
At TA = +25°C, RL = 100 Ω, VG = +1 V, and VIN = single-ended input on +VIN with –VIN at ground, unless otherwise noted.
40
1500
For > 40dB Gain Adjust Range
39
Quiescent Current (mA)
Feedback Resistor (W)
1400
1300
1200
1100
1000
900
NOTE: -3dB bandwidth varies with package type.
See the Application section for more details.
800
-IQ
37
+IQ
36
35
34
33
32
-1.0 -0.8 -0.6 -0.4 -0.2
700
1
38
10
100
0.2
0.4
0.6
0.8
1.0
Figure 8. Supply Current vs Control Voltage
(AVMAX = +2 V/V)
Figure 7. Recommended RF vs AVMAX
40
40
39
39
Quiescent Current (mA)
Quiescent Current (mA)
0
Gain Control Voltage (V)
AVMAX (V/V)
38
-IQ
37
36
+IQ
35
34
33
38
-IQ
37
36
+IQ
35
34
33
32
-1.0 -0.8 -0.6 -0.4 -0.2
0
0.2
0.4
0.6
0.8
32
-1.0 -0.8 -0.6 -0.4 -0.2
1.0
0
0.2
0.4
0.6
0.8
Gain Control Voltage (V)
Gain Control Voltage (V)
Figure 9. Supply Current vs Control Voltage
(AVMAX = +10 V/V)
Figure 10. Supply Current vs Control Voltage
(AVMAX = +100 V/V)
1.0
Input Offset Voltage (mV)
0
30
Input Bias Current (IB)
Right Scale
-0.5
25
20
-1.0
15
-1.5
10
5
-2.0
10x Input Offset Current (IOS)
Right Scale
-2.5
0
-3.0
Input Bias and Offset Current (mA)
0.5
35
VG = 0V
Input Offset Voltage (VOS)
Left Scale
1.0
-5
-50
-25
0
25
50
75
100
125
Temperature (°C)
Figure 11. Typical DC Drift vs Temperature
10
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7.8 Typical Characteristics: VS = ±5 V, AVMAX = +2 V/V
At TA = +25°C, RL = 100 Ω, RF = 1.33 kΩ, RG = 1.33 kΩ, VG = +1 V, VIN = single-ended input on +VIN with –VIN at ground, and
SOIC-14 package, unless otherwise noted.
3
400
0
300
Output Voltage (mV)
Normalized Gain (dB)
VO = 1VPP
-3
-6
-9
VO = 2VPP
-12
VO = 5VPP
VIN = 250mVPP
f = 20MHz
200
100
0
-100
-15
VO = 7VPP
-200
-18
1M
10M
100M
1G
-300
Time (10ns/div)
Frequency (Hz)
Figure 13. Small-Signal Pulse Response
Figure 12. Large-Signal Frequency Response
4
0.09
VIN = 2.5VPP
f = 20MHz
0.08
Output Voltage (V)
2
1
0
0.08
0.07
0.07
0.06
0.06
-dG
VG = 0V
0.05
-dP
VG = 1V
0.04
-dP
VG = 0V
0.03
0.05
0.04
0.03
-1
0.02
0.02
-2
0.01
0.01
0
0
1
-3
2
Magnitude (0.05dB/div)
0
-45
-0.05
-50
-0.10
-0.10
-0.15
-0.15
-0.20
-0.20
-0.25
-0.25
-0.30
-0.30
-0.35
-0.35
-0.40
-0.40
-0.45
-0.45
-0.50
-0.50
10
20
30
40
50
Deviation from Linear Phase (°)
AVMAX = +2V/V
VG = +1V
0
4
Figure 15. Composite Video dG/dP
Harmonic Distortion (dBc)
0
3
Number of Video Loads
Time (10ns/div)
Figure 14. Large-Signal Pulse Response
-0.05
Differential Phase (°)
Differential Gain (%)
3
0.09
-dG
VG = 1V
-55
-60
VG = +1V
AVMAX = +2V/V
VO = 2VPP
RL = 100W
2nd-Harmonic
-65
-70
3rd-Harmonic
-75
-80
-85
-90
-95
Frequency (MHz)
0.1
1
10
100
Frequency (MHz)
Figure 16. Gain Flatness, Deviation From Linear Phase
Figure 17. Harmonic Distortion vs Frequency
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Typical Characteristics: VS = ±5 V, AVMAX = +2 V/V (continued)
At TA = +25°C, RL = 100 Ω, RF = 1.33 kΩ, RG = 1.33 kΩ, VG = +1 V, VIN = single-ended input on +VIN with –VIN at ground, and
SOIC-14 package, unless otherwise noted.
-50
-60
Harmonic Distortion (dBc)
Harmonic Distortion (dBc)
2nd-Harmonic
-65
-70
-75
3rd-Harmonic
AVMAX = +2V/V
VG = +1V
VO = 2VPP
f = 20MHz
-80
-85
VG = +1V
AVMAX = +2V/V
RL = 100W
f = 20MHz
-55
-60
2nd-Harmonic
-65
-70
3rd-Harmonic
-75
-80
100
0.1
1k
1
Figure 18. Harmonic Distortion vs Load Resistance
VO = 2VPP
AVMAX = +2V/V
RL = 100W
f = 20MHz
-45
-50
Maximum Current Through RG Limited
2nd-Harmonic
-60
Figure 19. Harmonic Distortion vs
Output Voltage
45
Intercept Point (+dBm)
Harmonic Distortion (dBc)
-40
-55
40
35
30
25
-65
3rd-Harmonic
-70
-0.6
At 50W Matched Load
20
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1.0
0
10
Gain Control Voltage (V)
50
60
70
VG = 0VDC + 10mVPP
VIN = 0.5VDC
Constant Input Voltage
36
0
34
Constant Output Voltage
32
30
28
26
-0.4
-0.2
0
-3
-6
-9
fIN = 20MHz
At 50W Matched Load
20
-0.6
Normalized Gain (dB)
Intercept Point (+dBm)
40
3
38
0.2
0.4
0.6
0.8
1.0
-12
1M
Gain Control Voltage (V)
10M
100M
1G
Frequency (Hz)
Figure 22. Two-Tone, Third-Order Intermodulation Intercept
vs Gain Control Voltage
12
30
Figure 21. Two-Tone, Third-Order
Intermodulation Intercept
40
22
20
Frequency (MHz)
Figure 20. Harmonic Distortion vs
Gain Control Voltage
24
10
Output Voltage Swing (VPP)
Resistance (W)
Figure 23. Gain Control Frequency Response
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SBOS343D – SEPTEMBER 2007 – REVISED OCTOBER 2015
Typical Characteristics: VS = ±5 V, AVMAX = +2 V/V (continued)
At TA = +25°C, RL = 100 Ω, RF = 1.33 kΩ, RG = 1.33 kΩ, VG = +1 V, VIN = single-ended input on +VIN with –VIN at ground, and
SOIC-14 package, unless otherwise noted.
0
1.5
-1
1.0
0.5
0
VOUT (V)
1
Differential Input Voltage (VPP)
3
2
VG (V)
10
4
VIN = 1.25VDC
0
VG = 1V
-10
-20
-30
-40
VG = -1V
-50
-60
-70
-80
VO = 2VPP
-90
-0.5
-100
1M
-1.0
10M
1.6
1MHz
1.6
1.4
10MHz
Group Delay (ns)
Group Delay (ns)
1.4
1.2
20MHz
1.0
0.8
0.6
1.2
1.0
0.8
0.6
0.4
0.4
VG = +1V
VO = 1VPP
0.2
0.2
0
-1.0 -0.8 -0.6 -0.4 -0.2
0
0
0.2
0.4
0.6
0.8
1.0
0
20
40
Gain Control Voltage (V)
Figure 26. Group Delay vs Gain Control Voltage
0.1dB Flatness Targeted
0
10
100
80
100
Figure 27. Group Delay vs Frequency
Normalized Gain to Capacitive Load (dB)
10
1
60
Frequency (MHz)
100
RS (W)
1G
Figure 25. Fully-Attenuated Response
Figure 24. Gain Control Pulse Response
1.8
100M
Frequency (Hz)
Time (10ns/div)
1k
9
CL = 22pF
VO = 0.5VPP
CL = 10pF
6
3
CL = 47pF
0
CL = 100pF
-3
RF
-6
VIN
+VIN
RS
1.33kW
VOUT
VCA822
20W
-9
(1)
1kW
-VIN
NOTE: (1) 1kW is optional.
-12
1M
10M
100M
1G
Frequency (Hz)
Capacitive Load (pF)
Figure 28. Recommended RS vs Capacitive Load
Figure 29. Frequency Response vs Capacitive Load
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Typical Characteristics: VS = ±5 V, AVMAX = +2 V/V (continued)
10
1000
Input Voltage Noise Density (pA/ÖHz)
Output Voltage Noise Density (nV/ÖHz)
At TA = +25°C, RL = 100 Ω, RF = 1.33 kΩ, RG = 1.33 kΩ, VG = +1 V, VIN = single-ended input on +VIN with –VIN at ground, and
SOIC-14 package, unless otherwise noted.
VG = +1V
VG = 0V
100
VG = -1V
1
10
100
1k
10k
100k
1M
100
10M
1k
10k
100k
1M
10M
Frequency (Hz)
Frequency (Hz)
Figure 30. Output Voltage Noise Density
Figure 31. Input Current Noise Density
7.9 Typical Characteristics: VS = ±5 V, AVMAX = +10 V/V
3
3
0
0
Normalized Gain (dB)
Normalized Gain (dB)
At TA = +25°C, RL = 100 Ω, RF = 1 kΩ, RG = 200 Ω, VG = +1 V, and VIN = single-ended input on +VIN with –VIN at ground,
unless otherwise noted.
-3
VG = 1V
-6
-9
-12
AVMAX = 10V/V
VIN = 200mVPP
RL = 100W
-15
-18
-3
VO = 2VPP
-6
-9
VO = 5VPP
-12
VO = 7VPP
-15
VG = 0V
-18
1M
10M
100M
0
1G
50
200
250
300
350
400
3
300
VIN = 50mVPP
f = 20MHz
100
0
-100
VIN = 0.5VPP
f = 20MHz
2
Output Voltage (V)
200
Output Voltage (mV)
150
Figure 33. Large-Signal Frequency Response
Figure 32. Small-Signal Frequency Response
1
0
-1
-2
-200
-3
-300
Time (10ns/div)
Time (10ns/div)
Figure 34. Small-Signal Pulse Response
14
100
Frequency (MHz)
Frequency (Hz)
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Figure 35. Large-Signal Pulse Response
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SBOS343D – SEPTEMBER 2007 – REVISED OCTOBER 2015
Typical Characteristics: VS = ±5 V, AVMAX = +10 V/V (continued)
0.05
0.05
Magnitude (0.05dB/div)
0
-0.05
-0.05
-0.10
-0.10
-0.15
-0.15
-0.20
-0.20
-0.25
-0.25
VG = +1V
AVMAX = +10V/V
-0.30
-0.30
-0.35
-0.35
0
10
20
30
40
Deviation From Linear Phase (°)
0
Output Voltage Noise Density (nV/ÖHz)
At TA = +25°C, RL = 100 Ω, RF = 1 kΩ, RG = 200 Ω, VG = +1 V, and VIN = single-ended input on +VIN with –VIN at ground,
unless otherwise noted.
1000
VG = +1V
VG = 0V
100
VG = -1V
10
50
100
1k
10k
Frequency (MHz)
Figure 36. Gain Flatness, Deviation From Linear Phase
-50
Gain (dB)
-55
VG = +1V
AVMAX = +10V/V
VO = 2VPP
RL = 100W
2nd-Harmonic
-65
-70
3rd-Harmonic
-75
Figure 37. Output Voltage Noise Density
-80
-65
-70
3rd-Harmonic
-75
-80
-85
VG = +1V
AVMAX = +10V/V
VO = 2VPP
f = 20MHz
-90
-85
0.1
1
10
100
100
1k
Frequency (MHz)
Resistance (W)
Figure 38. Harmonic Distortion vs Frequency
Figure 39. Harmonic Distortion vs Load Resistance
-55
-45
-60
Harmonic Distortion (dBc)
Harmonic Distortion (dBc)
10M
2nd-Harmonic
-60
2nd-Harmonic
-65
-70
-75
1M
-60
Harmonic Distortion (dBc)
-45
100k
Frequency (Hz)
3rd-Harmonic
VG = +1V
AVMAX = +10V/V
RL = 100W
f = 20MHz
-50
-55
Max Current Through
RG Limited
-60
2nd-Harmonic
-65
3rd-Harmonic
-80
0.1
VO = 2VPP
AVMAX = +10V/V
RL = 100W
f = 20MHz
1
10
-70
-0.6
Output Voltage Swing (VPP)
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1.0
Gain Control Voltage (V)
Figure 40. Harmonic Distortion vs
Output Voltage
Figure 41. Harmonic Distortion vs
Gain Control Voltage
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Typical Characteristics: VS = ±5 V, AVMAX = +10 V/V (continued)
At TA = +25°C, RL = 100 Ω, RF = 1 kΩ, RG = 200 Ω, VG = +1 V, and VIN = single-ended input on +VIN with –VIN at ground,
unless otherwise noted.
40
45
40
35
30
34
32
Constant Input Voltage
30
28
26
25
24
22
At 50W Matched Load
20
5
10 15 20 25 30 35 40 45
50 55
60 65
At 50W Matched Load
20
-0.6
70
-0.4
0
-0.2
0.6
0.8
1.0
Figure 42. Two-Tone, Third-Order
Intermodulation Intercept
Figure 43. Two-Tone, Third-Order Intermodulation Intercept
vs Gain Control Voltage (fIN = 20 MHz)
6
11
10
9
8
7
6
5
VG = 0VDC + 10mVPP
VIN = 0.1VDC
3
4
3
0
-3
-6
-9
-12
-15
-1
-1.2
-18
-0.8
-0.4
0
0.4
0.8
1.2
1M
10M
Gain Control Voltage (V)
100M
1G
Frequency (Hz)
Figure 44. Gain vs Gain Control Voltage
Figure 45. Gain Control Frequency Response
4
5
3
4
1
0
1.5
-1
1.0
0.5
VOUT (V)
2
3
Output Voltage (V)
VIN = 0.25VDC
VG (V)
0.4
Gain Control Voltage (V)
2
1
0
2
100W
Load Line
1W Internal
Power Dissipation
25W
Load Line
1
0
50W
Load Line
-1
1W Internal
Power Dissipation
-2
-3
0
-4
-0.5
-5
-300
-1.0
-200
-100
0
100
200
300
Output Current (mA)
Time (10ns/div)
Figure 46. Gain Control Pulse Response
16
0.2
Frequency (MHz)
Normalized Gain (dB)
Gain (V/V)
Constant Output Voltage
36
Intercept Point (+dBm)
Intercept Point (+dBm)
38
Figure 47. Output Voltage and Current Limitations
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Typical Characteristics: VS = ±5 V, AVMAX = +10 V/V (continued)
2.0
30
20
10
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
8
1.5
VG = 1V
4
1.0
VIN (V)
0.5
Input-Referred
0
0
-0.5
VO = 2VPP
10M
Output Voltage
Right Scale
-1.0
VG = -1V
1M
100M
1G
-8
-2.0
Time (40ns/div)
Figure 49. IRG Limited Overdrive Recovery
Figure 48. Fully-Attenuated Response
2.0
8
1.85
6
1.80
1.0
4
1.75
0.5
2
0
-0.5
0
Input Voltage
Left Scale
-2
-1.0
Group Delay (ns)
1MHz
VOUT (V)
Input Voltage (V)
AVMAX = +10V/V
VG = 1.0V
Output Voltage
Right Scale
-4
-1.5
Frequency (Hz)
1.5
AVMAX = +10V/V
VG = -0.3V
Input Voltage
Left Scale
VOUT (V)
Gain (dB)
At TA = +25°C, RL = 100 Ω, RF = 1 kΩ, RG = 200 Ω, VG = +1 V, and VIN = single-ended input on +VIN with –VIN at ground,
unless otherwise noted.
10MHz
1.70
1.65
1.60
20MHz
-4
1.55
-1.5
-6
-2.0
-8
1.50
-1.0 -0.8 -0.6 -0.4 -0.2
Time (40ns/div)
0
0.2
0.4
0.6
0.8
1.0
Gain Control Voltage (V)
Figure 50. Output Limited Overdrive Recovery
Figure 51. Group Delay vs Gain Control Voltage
1.9
1.8
Group Delay (ns)
1.7
1.6
1.5
1.4
1.3
1.2
VG = +1V
VO = 1VPP
1.1
1.0
0
20
40
60
80
100
Frequency (MHz)
Figure 52. Group Delay vs Frequency
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7.10 Typical Characteristics: VS = ±5 V, AVMAX = +100 V/V
At TA = +25°C, RL = 100 Ω, RF = 845 Ω, RG = 16.9 Ω, VG = +1 V, VIN = single-ended input on +VIN with –VIN at ground, and
SOIC-14 package, unless otherwise noted.
3
3
VG = 1V
0
-3
-3
VG = 0V
Gain (dB)
Normalized Gain (dB)
0
-6
-9
-12
-9
VO = 7VPP
-12
AVMAX = 100V/V
VIN = 20mVPP
RL = 100W
-15
-18
-15
VO = 5VPP
-18
1
10
100
0
500
50
100
Figure 54. Large-Signal Frequency Response
3
VIN = 5mVPP
f = 20MHz
300
VIN = 50mVPP
f = 20MHz
Output Voltage (V)
2
100
0
-100
1
0
-1
-2
-300
-3
Time (10ns/div)
Time (10ns/div)
Figure 56. Large-Signal Pulse Response
0.10
0.1
0.05
0
0
-0.1
-0.05
-0.2
-0.10
-0.3
-0.15
-0.4
-0.20
-0.5
-0.25
-0.6
-0.30
-0.7
10
20
30
40
50
Deviation from Linear Phase (°)
VG = +1V
AVMAX = +100V/V
Output Voltage Noise Density (nV/ÖHz)
Figure 55. Small-Signal Pulse Response
Magnitude (0.05dV/div)
250
Figure 53. Small-Signal Frequency Response
-200
1000
VG = +1V
VG = 0V
100
VG = -1V
10
100
Frequency (MHz)
1k
10k
100k
1M
10M
Frequency (Hz)
Figure 57. Gain Flatness
18
200
Frequency (MHz)
200
0
150
Frequency (MHz)
300
Output Voltage (mV)
VO = 2VPP
-6
Figure 58. Output Voltage Noise Density
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Typical Characteristics: VS = ±5 V, AVMAX = +100 V/V (continued)
At TA = +25°C, RL = 100 Ω, RF = 845 Ω, RG = 16.9 Ω, VG = +1 V, VIN = single-ended input on +VIN with –VIN at ground, and
SOIC-14 package, unless otherwise noted.
-35
-45
-50
-55
2nd-Harmonic
-60
-65
-70
3rd-Harmonic
-75
-50
-55
-60
-80
-70
-75
-80
-90
1
10
3rd-Harmonic
-65
-85
0.1
2nd-Harmonic
-45
Harmonic Distortion (dBc)
-40
Harmonic Distortion (dBc)
-40
VG = +1V
AVMAX = +100V/V
VO = 2VPP
RL = 100W
100
VG = +1V
AVMAX = +100V/V
VO = 2VPP
f = 20MHz
100
1k
Frequency (MHz)
Resistance (W)
Figure 59. Harmonic Distortion vs Frequency
Figure 60. Harmonic Distortion vs Load Resistance
-30
-40
3rd-Harmonic
Harmonic Distortion (dBc)
Harmonic Distortion (dBc)
2nd-Harmonic
-45
-50
3rd-Harmonic
-55
VG = 1VPP
AVMAX = +100V/V
RL = 100W
f = 20MHz
-60
1
-50
Maximum Current Through RG Limited
-60
-70
10
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1.0
0.8
1.0
Gain Control Voltage (V)
Output Voltage Swing (VPP)
Figure 62. Harmonic Distortion vs
Gain Control Voltage
Figure 61. Harmonic Distortion vs
Output Voltage
33
31
31
29
29
Intercept Point (+dBm)
Intercept Point (+dBm)
VO = 2VPP
AVMAX = +100V/V
RL = 100W
f = 20MHz
2nd-Harmonic
-80
-0.6
-65
0.1
-40
27
25
23
21
19
Constant Input Voltage
27
25
Constant Output Voltage
23
21
19
17
17
At 50W Matched Load
15
5
10 15 20 25 30 35 40 45 50 55 60 65 70
At 50W Matched Load
15
-0.6 -0.4 -0.2
0
0.2
0.4
0.6
Frequency (MHz)
Gain Control Voltage (V)
Figure 63. Two-Tone, Third-Order
Intermodulation Intercept
Figure 64. Two-Tone, Third-Order Intermodulation Intercept
vs Gain Control Voltage (fIN = 20 MHz)
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Typical Characteristics: VS = ±5 V, AVMAX = +100 V/V (continued)
At TA = +25°C, RL = 100 Ω, RF = 845 Ω, RG = 16.9 Ω, VG = +1 V, VIN = single-ended input on +VIN with –VIN at ground, and
SOIC-14 package, unless otherwise noted.
3
110
-10
-1.2
VG = 0VDC + 10mVPP
VIN = 10mVDC
0
Normalized Gain (dB)
Gain (V/V)
100
90
80
70
60
50
40
30
20
10
0
Feedthrough
-3
-6
-9
-12
-0.8
-0.4
0
0.4
0.8
1M
1.2
10M
4
50
3
40
1
VOUT (V)
2
0
1.5
-1
1.0
VG (V)
2G
VG = 1V
30
Normalized Gain (dB)
VIN = 25mVDC
0.5
20
10
0
-10
-20
-30
VG = -1V
-40
0
VO = 2VPP
-50
-0.5
-60
1M
-1.0
10M
Time (10ns/div)
8
AVMAX = +100V/V
VG = -0.3V
0.20
8
AVMAX = +100V/V
VG = 1.0V
Output Voltage
Right Scale
0.15
0.4
4
0.10
4
0.2
2
0.05
2
0
0
0
0
-0.4
-2
Output Voltage
Right Scale
-0.6
-0.8
-0.05
-4
-0.10
-6
-0.15
-8
-0.20
6
-2
Input Voltage
Left Scale
Output Voltage (V)
-0.2
Output Voltage (V)
6
Input Voltage (V)
0.6
1G
Figure 68. Fully-Attenuated Response
Figure 67. Gain Control Pulse Response
Input Voltage
Left Scale
100M
Frequency (Hz)
0.8
Input Voltage (V)
1G
Figure 66. Gain Control Frequency Response
Figure 65. Gain vs Gain Control Voltage
-4
-6
-8
Time (40ns/div)
Time (40ns/div)
Figure 69. IRG Limited Overdrive Recovery
20
100M
Frequency (Hz)
Gain Control Voltage (V)
Figure 70. Output Limited Overdrive Recovery
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Typical Characteristics: VS = ±5 V, AVMAX = +100 V/V (continued)
At TA = +25°C, RL = 100 Ω, RF = 845 Ω, RG = 16.9 Ω, VG = +1 V, VIN = single-ended input on +VIN with –VIN at ground, and
SOIC-14 package, unless otherwise noted.
3.0
3.5
20MHz
3.0
2.0
10MHz
Group Delay (ns)
Group Delay (ns)
2.5
1MHz
1.5
1.0
0.5
2.5
2.0
1.5
1.0
VG = +1V
VO = 1VPP
0.5
0
-1.0 -0.8 -0.6 -0.4 -0.2
0
0
0.2
0.4
0.6
0.8
1.0
0
20
40
60
80
Gain Control Voltage (V)
Frequency (MHz)
Figure 71. Group Delay vs Gain Control Voltage
Figure 72. Group Delay vs Frequency
100
8 Parameter Measurement Information
+VIN
VIN
R1
50W
Source
RF
RG+
50W
RG
VOUT
RGR3
R2
50W
Load
-VIN
50W
VG
Figure 73. Test Circuit
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9 Detailed Description
9.1 Overview
The VCA822 is a voltage controlled variable gain amplifier with differential inputs and a single ended output. The
maximum gain is set by external resistors while the gain range is controlled by an external analog voltage. The
maximum gain is designed for gains of 2 V/V up to 100 V/V and the analog control allows a gain range of over
40 dB. The VCA822 input consists of two buffers which together create a fully symmetrical, high impedance
differential input with a typical common mode rejection of 80 dB. The gain set resistor is connected between the
two input buffer output pins, so that the input impedance is independent of the gain settings. The bipolar inputs
have a input voltage range of +1.6 and –2.1 V on ±5 V supplies. The amplifier maximum gain is set by external
resistors, but the internal gain control circuit is controlled by a continuously variable, analog voltage. The gain
control is a multiplier stage which is linear in V/V. The gain control input pin operates over a 2-V voltage range
(–1 V to +1 V). The VCA822 contains a high speed, high current output buffer. The output stage can typically
swing ±3.9 V and source/sink ±160 mA. The VCA822 can be operated over a voltage range of ±3.5 V to ±6 V.
9.2 Feature Description
The VCA822 can be operated with both single ended or differential input signals. The inputs present consistently
high impedance across all gain configurations. By using an analog control signal the amplifier gain is
continuously variable for smooth, glitch free gain changes. With a large signal bandwidth of 137 Mhz and a slew
rate of 1700 V/us the VCA822 offers linear performance over a wide range of signal amplitudes and gain
settings. The low impedance/high current output buffer can drive loads ranging from low impedance transmission
lines to high-impedance, switched-capacitor analog to digital converters. By using closely matched internal
components the VCA822 offers a typical gain accuracy of ±0.1 dB.
9.3 Device Functional Modes
The VCA822 functions as a differential input, single-ended output variable gain amplifier. This functional mode is
enabled by applying power to the amplifier supply pins and is disabled by turning the power off.
The gain is continuously variable through the analog gain control input. While the gain range is fixed the
maximum gain is set by two external components, Rf and Rg as shown in the Parameter Measurement
Information. The maximum gain is equal to 2x (Rf / Rg). This gain is achieved with a 2-V voltage on the gain
adjust pin VG. As the voltage decreases on the VG pin, the gain decreases in a linear in dB fashion with over 40
dB of gain range from 2-V to 0-V control voltage.
As with most other differential input amplifiers, inputs can be applied to either one or both of the amplifier inputs.
The amplifier gain is controlled through the gain control pin.
9.3.1 Maximum Gain of Operation
This section describes the use of the VCA822 device in a fixed-gain application in which the VG control pin is set
at VG = +1 V. The tradeoffs described here are with bandwidth, gain, and output voltage range.
In the case of an application that does not make use of the VGAIN, but requires some other characteristic of the
VCA822, the RG resistor must be set such that the maximum current flowing through the resistance IRG is less
than ±2.6 mA typical, or 5.2 mAPP as defined in Electrical Characteristics: VS = ±5 V, and must follow Equation 1.
VOUT
IRG =
AVMAX ´ RG
(1)
As demonstrated by Equation 1, when the output dynamic range and maximum gain are defined, the gain
resistor is set. This gain setting in turn affects the bandwidth because in order to achieve the gain (and with a set
gain element), the feedback element of the output stage amplifier is set as well. Keeping in mind that the output
amplifier of the VCA822 device is a current-feedback amplifier, the larger the feedback element, the lower the
bandwidth as the feedback resistor is the compensation element.
Limiting the discussion to the input voltage only and ignoring the output voltage and gain, Figure 1 illustrates the
tradeoff between the input voltage and the current flowing through the gain resistor.
22
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Device Functional Modes (continued)
9.3.2 Output Current and Voltage
The VCA822 device provides output voltage and current capabilities that are unsurpassed in a low-cost
monolithic VCA. Under no-load conditions at +25°C, the output voltage typically swings closer than 1 V to either
supply rails; the +25°C swing limit is within 1.2 V of either rails. Into a 15-Ω load (the minimum tested load), it is
tested to deliver more than ±160 mA.
The specifications described previously, though familiar in the industry, consider voltage and current limits
separately. In many applications, it is the voltage × current, or V-I product, that is more relevant to circuit
operation. Refer to the Output Voltage and Current Limitations plot (Figure 47) in the Typical Characteristics
section. The X-axis and Y-axis of this graph show the zero-voltage output current limit and the zero-current
output voltage limit, respectively. The four quadrants give a more detailed view of the VCA822 device output
drive capabilities, noting that the graph is bounded by a Safe Operating Area of 1-W maximum internal power
dissipation. Superimposing resistor load lines onto the plot shows that the VCA822 device can drive ±2.5 V into
25 Ω or ±3.5 V into 50 Ω without exceeding the output capabilities or the 1 W dissipation limit. A 100-Ω load line
(the standard test circuit load) shows the full ±3.9 V output swing capability, as shown in the Typical
Characteristics.
The minimum specified output voltage and current over-temperature are set by worst-case simulations at the
cold temperature extreme. Only at cold start-up do the output current and voltage decrease to the numbers
shown in Electrical Characteristics: VS = ±5 V. As the output transistors deliver power, the respective junction
temperatures increase, increasing the available output voltage swing, and increasing the available output current.
In steady-state operation, the available output voltage and current is always greater than that temperature shown
in the over-temperature specifications because the output stage junction temperatures are higher than the
specified operating ambient.
9.3.3 Input Voltage Dynamic Range
The VCA822 device has a input dynamic range limited to +1.6 V and –2.1 V. Increasing the input voltage
dynamic range can be done by using an attenuator network on the input. If the VCA822 device is trying to
regulate the amplitude at the output, such as in an AGC application, the input voltage dynamic range is directly
proportional to Equation 2.
VIN(PP) = RG ´ IRG(PP)
(2)
As such, for unity-gain or under-attenuated conditions, the input voltage must be limited to the CMIR of ±1.6 V
(3.2 VPP) and the current (IRQ) must flow through the gain resistor, ±2.6 mA (5.2 mAPP). This configuration sets a
minimum value for RE such that the gain resistor has to be greater than Equation 3.
3.2VPP
RGMIN =
= 615.4W
5.2mAPP
(3)
Values lower than 615.4Ω are gain elements that result in reduced input range, as the dynamic input range is
limited by the current flowing through the gain resistor RG (IRG). If the IRG current is limiting the performance of
the circuit, the input stage of the VCA822 device goes into overdrive, resulting in limited output voltage range.
Such IRG-limited overdrive conditions are shown in Figure 49 for the gain of +10 V/V and Figure 69 for the +100
V/V gain.
9.3.4 Output Voltage Dynamic Range
With its large output current capability and its wide output voltage swing of ±3.9-V typical on a 100-Ω load, it is
easy to forget other types of limitations that the VCA822 device can encounter. For these limitations, careful
analysis must be done to avoid input stage limitation, either voltage or IRG current; also, consider the gain
limitation, as the control pin VG varies, affecting other aspects of the circuit.
9.3.5 Bandwidth
The output stage of the VCA822 device is a wideband current-feedback amplifier. As such, the feedback
resistance is the compensation of the last stage. Reducing the feedback element and maintaining the gain
constant limits the useful range of IRG, and therefore reducing the gain adjust range. For a given gain, reducing
the gain element limits the maximum achievable output voltage swing.
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Device Functional Modes (continued)
9.3.6 Offset Adjustment
As a result of the internal architecture used on the VCA822 device, the output offset voltage originates from the
output stage and from the input stage and multiplier core. Figure 91 shows how to compensate both sources of
the output offset voltage. Use this procedure to compensate the output offset voltage: starting with the output
stage compensation, set VG = –1 V to eliminate all offset contribution of the input stage and multiplier core.
Adjust the output stage offset compensation potentiometer. Finally, set VG = +1 V to the maximum gain and
adjust the input stage and multiplier core potentiometer. This procedure effectively eliminates all offset
contribution at the maximum gain. Because adjusting the gain modifies the contribution of the input stage and the
multiplier core, some residual output offset voltage remains.
9.3.7 Noise
The VCA822 device offers 8.2 nV/√Hz input-referred voltage noise density at a gain of +10 V/V and 1.8 pA/√Hz
input-referred current noise density. The input-referred voltage noise density considers that all noise terms,
except the input current noise but including the thermal noise of both the feedback resistor and the gain resistor,
are expressed as one term.
This model is formulated in Equation 4 and Figure 90.
eO = AVMAX ´
2 ´ (RS ´ in)2 + en2 + 2 ´ 4kTRS
(4)
A more complete model is shown in Figure 92. For additional information on this model and the actual modeled
noise terms, please contact the High-Speed Product Application Support team at www.ti.com.
9.3.8 Input and ESD Protection
The VCA822 device is built using a very high-speed complementary bipolar process. The internal junction
breakdown voltages are relatively low for these very small geometry devices. These breakdowns are reflected in
Absolute Maximum Ratings.
All pins on the VCA822 device are internally protected from ESD by means of a pair of back-to-back reversebiased diodes to either power supply, as shown in Figure 74. These diodes begin to conduct when the pin
voltage exceeds either power supply by about 0.7 V. This situation can occur with loss of the amplifier power
supplies while a signal source is still present. The diodes can typically withstand a continuous current of 30 mA
without destruction. To ensure long-term reliability, however, diode current should be externally limited to 10 mA
whenever possible.
+VS
ESD protection diodes internally
connected to all pins.
External
Pin
Internal
Circuitry
-VS
Figure 74. Internal ESD Protection
24
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10 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
10.1 Application Information
The VCA822 has flexible maximum gain which is set by the Rf and Rg resistors shown in Parameter
Measurement Information. The maximum gain is equal to 2x (Rf / Rg). This gain is achieved with a 2-V voltage
on the gain adjust pin VG. As the voltage decreases on the VG pin, the gain decreases in a linear in dB fashion
with over 40 dB of gain range from 2-V to 0-V control voltage.
10.1.1 Design-In Tools
10.1.1.1 Demonstration Boards
Two printed circuit boards (PCBs) are available to assist in the initial evaluation of circuit performance using the
VCA822 device in the two package options. Both of these are offered from ti.com as unpopulated PCBs,
delivered with a user's guide. The summary information for these fixtures is shown in Table 1.
Table 1. EVM Ordering Information
PRODUCT
PACKAGE
BOARD PART NUMBER
LITERATURE NUMBER
VCA822ID
SOIC-14
DEM-VCA-SO-1B
SBOU050
VCA822IDGS
MSOP-10
DEM-VCA-MSOP-1A
SBOU051
The demonstration fixtures can be requested at the TI's web site through the VCA822 device product folder.
10.1.1.2 Macromodels and Applications Support
Computer simulation of circuit performance using SPICE is often useful when analyzing the performance of
analog circuits and systems. This principle is particularly true for video and RF amplifier circuits where parasitic
capacitance and inductance can play a major role in circuit performance. A SPICE model for the VCA822 device
is available through the TI web page. The applications group is also available for design assistance. The models
available from TI predict typical small-signal ac performance, transient steps, dc performance, and noise under a
wide variety of operating conditions. The models include the noise terms found in the electrical specifications of
the relevant product data sheet.
10.1.1.3 Operating Suggestions
Operating the VCA822 device optimally for a specific application requires trade-offs between bandwidth, input
dynamic range and the maximum input voltage, the maximum gain of operation and gain, output dynamic range
and the maximum input voltage, the package used, loading, and layout and bypass recommendations. The
Typical Characteristics have been defined to cover as much ground as possible to describe the VCA822 device
operation. There are four sections in the Typical Characteristics:
• VS = ±5 V DC Parameters and VS = ±5 V DC and Power-Supply Parameters, which include dc operation and
the intrinsic limitation of a VCA822 device design
• VS = ± 5 V, AVMAX = +2 V/V Gain of +2V/V Operation
• VS = ±5 V, AVMAX = +10 V/V Gain of +10V/V Operation
• VS = ±5 V, AVMAX = +100 V/V Gain of +100V/V Operation
Where the Typical Characteristics describe the actual performance that can be achieved by using the amplifier
properly, the following sections describe in detail the trade-offs needed to achieve this level of performance.
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10.1.1.4 Package Considerations
The VCA822 device is available in both SOIC-14 and MSOP-10 packages. Each package has, for the different
gains used in the typical characteristics, different values of RF and RG to achieve the same performance detailed
in Electrical Characteristics: VS = ±5 V.
Figure 73 shows a test gain circuit for the VCA822 device. Table 2 lists the recommended configuration for the
SOIC-14 and MSOP-10 package.
Table 2. SOIC-14 and MSOP-10 RF and RG Configurations
G=2
G = 10
G = 100
RF
1.33 kΩ
1 kΩ
845 Ω
RG
1.33 kΩ
200 Ω
16.9 Ω
There are no differences between the packages in the recommended values for the gain and feedback resistors.
However, the bandwidth for the VCA822IDGS (MSOP-10 package) is lower than the bandwidth for the
VCA822ID (SOIC-14 package). This difference is true for all gains, but especially true for gains greater than 5
V/V, as can be seen in Figure 75 and Figure 76.
NOTE
The scale must be changed to a linear scale to view the details.
3
0
AVMAX = 2V/V
-3
AVMAX = 5V/V
-6
AVMAX = 10V/V
AVMAX = 20V/V
-9
Normalized Gain (dB)
Normalized Gain (dB)
3
0
AVMAX = 10V/V
AVMAX = 2V/V
-3
AVMAX = 20V/V
-6
AVMAX = 50V/V
-9
AVMAX = 50V/V
AVMAX = 100V/V
AVMAX = 5V/V
AVMAX = 100V/V
-12
-12
0
26
50
100
150
200
0
50
100
150
200
Frequency (MHz)
Frequency (MHz)
Figure 75. SOIC-14 Recommended RF and RG vs AVMAX
Figure 76. MSOP-10 Recommended RF and RG vs AVMAX
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10.2 Typical Applications
10.2.1 Wideband Variable Gain Amplifier Operation Application
+5V
0.1mF
X2Yâ
Capacitor
-5V
+
2.2mF
+ 2.2mF
VG
+VIN
VIN
20W
x1
IRG
RG+
RG
200W
FB
RF
1kW
x2
RG-
VOUT
VOUT
x1
20W
-VIN
VREF
VCA822
20W
Figure 77. DC-Coupled, AVMAX = +10 V/V, Bipolar Supply Specification and Test Circuit
10.2.1.1 Design Requirements
The design shown in Figure 77 requires a single-ended input, continuously variable gain control and a singleended output. This configuration is used to achieve the best performance with a bipolar supply. This circuit also
requires a maximum gain of 10 V/V and low noise.
10.2.1.2 Detailed Design Procedure
The VCA822 device provides an exceptional combination of high output power capability with a wideband,
greater than 40-dB gain adjust range, linear in V/V variable gain amplifier. The input stage of the VCA822 device
places the transconductance element between two input buffers, using the output currents as the forward signal.
As the differential input voltage rises, a signal current is generated through the gain element. This current is then
mirrored and gained by a factor of two before reaching the multiplier. The other input of the multiplier is the
voltage gain control pin, VG. Depending on the voltage present on VG, up to two times the gain current is
provided to the transimpedance output stage. The transimpedance output stage is a current-feedback amplifier
providing high output current capability and high slew rate, 1700 V/μs. This exceptional full-power performance
comes at the price of a relatively high quiescent current (36 mA), but a low input voltage noise for this type of
architecture (8.2 nV/√Hz).
Figure 77 shows the dc-coupled, gain of +10 V/V, dual power-supply circuit used as the basis of the ±5 V
Electrical Characteristics: VS = ±5 V and Typical Characteristics: VS = ±5 V, DC Parameters. For test purposes,
the input impedance is set to 50 Ω with a resistor to ground and the output impedance is set to 50 Ω with a
series output resistor. Voltage swings reported in Electrical Characteristics: VS = ±5 V are taken directly at the
input and output pins, while output power (dBm) is at the matched 50-Ω load. For the circuit in Figure 77, the
total effective load is 100 Ω ∥ 1 kΩ.
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NOTE
For the SOIC-14 package, there is a voltage reference pin, VREF (pin 9). For the SOIC-14
package, this pin must be connected to ground through a 20-Ω resistor in order to avoid
possible oscillations of the output stage. In the MSOP-10 package, this pin is internally
connected and does not require such precaution. An X2Y® capacitor has been used for
power-supply bypassing. The combination of low inductance, high resonance frequency,
and integration of three capacitors in one package (two capacitors to ground and one
across the supplies) of this capacitor enables to achieve the low second-harmonic
distortion reported in Electrical Characteristics: VS = ±5 V.
More information on how the VCA822 device operates can be found in the Operating Suggestions section.
10.2.1.3 Application Curve
2.2
2.0
1.8
1.6
3
-3
VG = 0V
Gain (V/V)
Normalized Gain (dB)
0
-6
-9
VG = 1V
-12
-15
AVMAX = 2V/V
VIN = 1VPP
RL = 100W
-18
1M
10M
100M
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
-0.2
-1.2
1G
-0.8
-0.4
0
0.4
0.8
1.2
Gain Control Voltage (V)
Frequency (Hz)
Figure 79. Gain vs Gain Control Voltage
Figure 78. Small-Signal Frequency Response
10.2.2 Four-Quadrant Multiplier Application
R1
VG
RF
VIN
RS
Source
Impedance
+VIN
RG+
FB
VCA822
R2
RG
RG-VIN
R3
20W
Figure 80. Four-Quadrant Multiplier Circuit
10.2.2.1 Design Requirements
A multiplier requires two inputs, one for the X input and one for the Y input. The output of the multiplier circuit is
in the form of VOUT = aVin1 × bVin2 : where a and b are real numbers and should not be negative. For four
quadrant operation both positive and negative inputs must be supported on the X and Y inputs.
10.2.2.2 Detailed Design Procedure
A four-quadrant multiplier can easily be implemented using the VCA822. By placing a resistor between FB and
VIN, the transfer function depends upon both VIN and VG, as shown in Equation 5.
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RF
RG
´ VG ´ VIN +
RF
RF
RG
-
´ VIN
R1
(5)
Setting R1 to equal RG, the term that depends only on VIN drops out of the equation, leaving only the term that
depends on both VG and VIN. VOUT then follows Equation 6.
RF
VOUT =
´ VIN ´ VG
RG
(6)
The behavior of this circuit is illustrated in Figure 81. Keeping the input amplitude of a 1MHz signal constant and
varying the VG voltage (100kHz, 2VPP) gives the modulated output voltage shown in Figure 81.
10.2.2.3 Application Curves
1.5
fIN = 1MHz
fVG = 0.1MHz
Amplitude (V)
1.0
0.5
0
-0.5
VIN
VOUT
-1.0
VG
-1.5
0
1
2
3
4
5
6
7
8
9
10
Time (ms)
Figure 81. Modulated Output Signal of the Four-Quadrant Multiplexer Circuit
10.2.3 Difference Amplifier Application
RF
VIN+
+VIN
RG+
RS
RG
FB
VCA822
RG-VIN
VIN-
20W
RS
Figure 82. Difference Amplifier
10.2.3.1 Design Requirements
For a difference amplifier, the design requirements are differential voltage gain, common mode rejection, and
load drive capability. This circuit delivers differential gain of 2* (Rf/Rg), and CMRR as shown in Figure 83.
10.2.3.2 Detailed Design Procedure
Because both inputs of the VCA822 device are high-impedance, a difference amplifier can be implemented
without any major problem. This implementation is shown in Figure 82. This circuit provides excellent commonmode rejection ratio (CMRR) as long as the input is within the CMRR range of –2.1 V to +1.6 V. Note that this
circuit does not make use of the gain control pin, VG. Also, it is recommended to choose RS such that the pole
formed by RS and the parasitic input capacitance does not limit the bandwidth of the circuit. The common-mode
rejection ratio for this circuit implemented in a gain of +10 V/V for VG = +1 V is shown in Figure 83. Note that
because the gain control voltage is fixed and is normally set to +1 V, the feedback element can be reduced in
order to increase the bandwidth. When reducing the feedback element make sure that the VCA822 device is not
limited by common-mode input voltage, the current flowing through RG, or any other limitation described in this
data sheet.
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10.2.3.3 Application Curve
Common-Mode Rejection Ratio (dB)
95
90
85
80
75
70
65
60
55
50
45
Input-Referred
40
100k
1M
10M
100M
Frequency (Hz)
Figure 83. Common-Mode Rejection Ratio
10.2.4 Differential Equalizer Application
VIN1
RF
+VIN
RG+
RS
R1
FB
RG
VCA822
C1
RGVIN2
-VIN
20W
RS
Figure 84. Differential Equalizer
10.2.4.1 Design Requirements
Signals that travel over a length of cable experience an attenuation that is proportional to the square root of the
frequency. For this reason, a fixed bandwidth amplifier will not restore the original signal. To replicate the original
signal, the higher frequency signal components require more gain. The circuit in Figure 84 has one stage of
frequency shaping to help restore a signal transmitted along a cable. If needed, additional frequency shaping
stages can be added as shown in Figure 85.
10.2.4.2 Detailed Design Procedure
If the application requires frequency shaping (the transition from one gain to another), the VCA822 device can be
used advantageously because its architecture allows the application to isolate the input from the gain setting
elements. Figure 84 shows an implementation of such a configuration. The transfer function is shown in
Equation 7.
RF
1 + sRGC1
´
G=2´
RG
1 + sR1C1
(7)
This transfer function has one pole, P1 (located at RGC1), and one zero, Z1 (located at R1C1). When equalizing an
RC load, RL and CL, compensate the pole added by the load located at RLCL with the zero Z1. Knowing RL, CL,
and RG allows the user to select C1 as a first step and then calculate R1. Using RL = 75 Ω, CL = 100 pF and
wanting the VCA822 device to operate at a gain of +2V/V, which gives RF = RG = 1.33 kΩ, allows the user to
select C1 = 5 pF to ensure a positive value for the resistor R1. With all these values known, R1 can be calculated
to be 170 Ω. The frequency response for both the initial, unequalized frequency response and the resulting
equalized frequency response are shown in Figure 85.
30
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10.2.4.3 Application Curve
9
Equalized Frequency
Response
6
3
Gain (dB)
0
-3
-6
Initial Frequency Response
of VCA822 with RC Load
-9
-12
-15
-18
-21
-24
10M
1M
100M
1G
Frequency (Hz)
Figure 85. Differential Equalization of an RC Load
10.2.5 Differential Cable Equalizer Application
VIN
R2
1.33kW
+VIN
R8
50W
RG+
R18
40kW
R17
17.5kW
R21
8.7kW
R9
1.27kW
R9
1.27kW
C7
100nF
VCA822
RG-VIN
C6
120nF
VOUT
FB
VREF
GND
VG
R1
20W
R10
75W
VOUT
75W Load
R5
50W
C5
1.42pF
VG = +1VDC
C9
10mF
Figure 86. Differential Cable Equalizer
10.2.5.1 Design Requirements
Signals that travel over a length of cable experience an attenuation that is proportional to the square root of the
frequency. For this reason, a fixed bandwidth amplifier will not restore the original signal. To replicate the original
signal, the higher frequency signal components require more gain. The circuit in Figure 86 has multiple stages of
frequency shaping to help restore a signal transmitted along a cable. This circuit is similar to the one shown in
Figure 84, but is much more accurate in replicating the 1/(sqrt(f)) frequency response shape.
10.2.5.2 Detailed Design Procedure
A differential cable equalizer can easily be implemented using the VCA822. An example of a cable equalization
for 100 feet of Belden Cable 1694F is illustrated in Figure 86, with the result for this implementation shown in
Figure 87. This implementation has a maximum error of 0.2dB from dc to 40MHz.
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10.2.5.3 Application Curve
2.0
1694F Cable Attenuation (dB)
Equalizer Gain (dB)
Cable Attenuations
1.5
1.0
VCA822 with
Equalization
0.5
0
-0.5
-1.0
1
100
10
Frequency (MHz)
Figure 87. Cable Attenuation versus Equalizer Gain
NOTE
This implementation shows the cable attenuation side-by-side with the equalization in the
same plot. For a given frequency, the equalization function realized with the VCA822
device matches the cable attenuation. The circuit in Figure 86 is a driver circuit. To
implement a receiver circuit, the signal is received differentially between the +VIN and –VIN
inputs.
10.2.6 Voltage-Controlled Low-Pass Filter Application
R2
332W
24pF
C
R1
332W
RF
1kW
VIN
24pF
+VIN
RG+
OPA690
RG
200W
FB
VCA822 Out
RG-VIN
50W
VOUT
20W
VG
Figure 88. Voltage-Control Low-Pass Filter
10.2.6.1 Design Requirements
A low pass filter should be DC coupled and should only pass frequencies up to the cut off frequency. A good
filter provides increasing attenuation as the frequency increases above the cutoff frequency as well as a flat
frequency response over the range of frequencies below the cutoff frequency. Passive filters have the limitation
of a fixed cutoff frequency unless variable capacitors or inductors are used. This circuit uses the variable gain of
the VCA822 to provide an electronically controlled cutoff frequency.
10.2.6.2 Detailed Design Procedure
In the circuit of Figure 88, the VCA822 device serves as the variable-gain element of a voltage-controlled lowpass filter. This section discusses how this implementation expands the circuit voltage swing capability over that
normally achieved with the equivalent multiplier implementation. The circuit control voltage, VG, is calculated as
according to the simplified relationship in Equation 8:
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VOUT
VIN
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=-
R2
R1
1
´
1+s
R 2C
(8)
G
The response control results from amplification of the feedback voltage applied to R2. First, consider the case
where the VCA822 device produces G = 1V/V. Then this circuit performs as if the amplifier were replaced by a
short circuit. Visually replacing the amplifier by a short leaves a simple voltage-feedback amplifier with a
feedback resistor bypassed by a capacitor. Replacing this gain with a variable gain, G, the pole can be written as
shown in Equation 9:
G
f8 =
2pR2C
(9)
Because the VCA822 device is most linear in the midrange, the median of the adjustable pole should be set at
VG = 0V (see Figure 79, Figure 42, Figure 63, and Equation 10). Selecting R1 = R2 = 332 Ω, and targeting a
median frequency of 10 MHz, the capacitance (C) is 24 pF. Because the OPA690 was selected for the circuit of
Figure 88, and in order to limit peaking in the OPA690 frequency response, a capacitor equal to C was added on
the inverting mode to ground. This architecture has the effect of setting the high-frequency noise gain of the
OPA690 to +2 V/V, ensuring stability and providing flat frequency response.
-0.8V £ VG £ 0.8V
(10)
Once the median frequency is set, the maximum and minimum frequencies can be determined by using VG =
–0.8V and VG = +0.8 V in the gain equation of Equation 11. Note that this is a first-order analysis and does not
take into consideration the open-loop gain limitation of the OPA690.
RF
VG + 1
G=2´
´
RG
2
(11)
With the components shown, the circuit provides a linear variation of the low-pass cutoff from 2MHz to 20MHz,
using –1V ≤ VG ≤ +1V. Practical evaluation shows that this circuit works from 8 MHz to 16 MHz with –0.8V < VG
< +0.8 V, as shown in Figure 89.
10.2.6.3 Application Curve
3
VG = +0.8V
0
-3
VG = +0.5V
Gain (dB)
-6
-9
VG = 0V
-12
VG = -0.5V
-15
-18
VG = -0.8V
-21
VOUT = 1VPP
-24
0
25
50
75
100
125
150
175
200
Frequency (MHz)
Figure 89. VCA822 as a Voltage-Control, Low-Pass Filter
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10.3 System Examples
RF
in
RS
+VIN
RG+
eO
RG
*
FB
eO
VCA822
RG-VIN
4kTRS
in
RS
*
4kTRS
NOTE: RF and RG are noiseless.
Figure 90. Simple Noise Model
+5V
Output Stage Offset
Compensation Circuit
10kW
4kW
0.1mF
-5V
RF
VIN
+VIN
RG+
50W
RG
FB
VOUT
VCA822
RG-VIN
+5V
1kW
50W
10kW
0.1mF
-5V
Input Stage and Multiplexer Core
Offset Compensation Circuit
Figure 91. Adjusting the Input and Output Voltage Sources
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System Examples (continued)
VG
inINPUT
VG
+VIN
V+
RS1
*
*
enINPUT
4kTRS1
FB
x1
RF
+RG
*
inINPUT
VOUT
RG
(Noiseless)
ICORE
eO
iinOUTPUT
-RG
VREF
x1
RF
enOUTPUT
-VIN
VRS2
4kTRF
*
*
enINPUT
iniOUTPUT
*
4kTRF
inINPUT
GND
*
4kTRS2
Figure 92. Full Noise Model
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11 Power Supply Recommendations
High-speed amplifiers require low inductance power supply traces and low ESR bypass capacitors. The power
supply voltage should be centered on the desired amplifier output voltage, so for ground referenced output
signals, split supplies are required. The power supply voltage should be from 7 V to 12 V.
12 Layout
12.1 Layout Guidelines
Achieving optimum performance with a high-frequency amplifier such as the VCA822 device requires careful
attention to printed circuit board (PCB) layout parasitics and external component types. Recommendations to
optimize performance include:
a. Minimize parasitic capacitance to any AC ground for all of the signal I/O pins. This recommendation
includes the ground pin (pin 2). Parasitic capacitance on the output can cause instability: on both the
inverting input and the noninverting input, it can react with the source impedance to cause unintentional band
limiting. To reduce unwanted capacitance, a window around the signal I/O pins should be opened in all of the
ground and power planes around those pins. Otherwise, ground and power planes should be unbroken
elsewhere on the board. Place a small series resistance (greater than 25 Ω) with the input pin connected to
ground to help decouple package parasitics.
b. Minimize the distance (less than 0.25”) from the power-supply pins to high-frequency 0.1-μF decoupling
capacitors. At the device pins, the ground and power plane layout should not be in close proximity to the
signal I/O pins. Avoid narrow power and ground traces to minimize inductance between the pins and the
decoupling capacitors. The power-supply connections should always be decoupled with these capacitors.
Larger (2.2-μF to 6.8-μF) decoupling capacitors, effective at lower frequencies, should also be used on the
main supply pins. These capacitors may be placed somewhat farther from the device and may be shared
among several devices in the same area of the PCB.
c. Careful selection and placement of external components preserve the high-frequency performance of the
VCA822. Resistors should be a very low reactance type. Surface-mount resistors work best and allow a
tighter overall layout. Metal-film and carbon composition, axially-leaded resistors can also provide good highfrequency performance. Again, keep the leads and PCB trace length as short as possible. Never use wirewound type resistors in a high-frequency application. Because the output pin is the most sensitive to parasitic
capacitance, always position the series output resistor, if any, as close as possible to the output pin. Other
network components, such as inverting or non-inverting input termination resistors, should also be placed
close to the package.
d. Connections to other wideband devices on the board may be made with short direct traces or through
onboard transmission lines. For short connections, consider the trace and the input to the next device as a
lumped capacitive load. Relatively wide traces (50 mils to 100 mils, or 1.27 mm to 2.54 mm) should be used,
preferably with ground and power planes opened up around them.
e. Socketing a high-speed part like the VCA822 device is not recommended. The additional lead length
and pin-to-pin capacitance introduced by the socket can create an extremely troublesome parasitic network,
which can make it almost impossible to achieve a smooth, stable frequency response. Best results are
obtained by soldering the VCA822 device onto the board.
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12.2 Layout Example
Figure 93. Layout Recommendation
12.3 Thermal Considerations
The VCA822 device does not require heat-sinking or airflow in most applications. The maximum desired junction
temperature sets the maximum allowed internal power dissipation as described in this section. In no case should
the maximum junction temperature be allowed to exceed +150°C.
Operating junction temperature (TJ) is given by Equation 12.
TJ = TA + PD ´ qJA
(12)
The total internal power dissipation (PD) is the sum of quiescent power (PDQ) and additional power dissipated in
the output stage (PDL) to deliver load power. Quiescent power is simply the specified no-load supply current
times the total supply voltage across the part. PDL depends on the required output signal and load; for a
grounded resistive load, however, it is at a maximum when the output is fixed at a voltage equal to one-half of
either supply voltage (for equal bipolar supplies). Under this worst-case condition, PDL = VS 2 / (4 × RL), where RL
is the resistive load.
Note that it is the power in the output stage and not in the load that determines internal power dissipation. As a
worst-case example, compute the maximum TJ using a VCA822ID (SOIC-14 package) in the circuit of Figure 77
operating at maximum gain and at the maximum specified ambient temperature of +85°C.
2
PD = 10V(38mA) + 5 /(4 ´ 100W) = 442.5mW
(13)
Maximum TJ = +85°C + (0.449W ´ 80°C/W) = 120.5°C
(14)
This maximum operating junction temperature is well below most system level targets. Most applications should
be lower because an absolute worst-case output stage power was assumed in this calculation of VCC / 2, which
is beyond the output voltage range for the VCA822 device.
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13 Device and Documentation Support
13.1 Device Support
13.1.1 Third-Party Products Disclaimer
TI'S PUBLICATION OF INFORMATION REGARDING THIRD-PARTY PRODUCTS OR SERVICES DOES NOT
CONSTITUTE AN ENDORSEMENT REGARDING THE SUITABILITY OF SUCH PRODUCTS OR SERVICES
OR A WARRANTY, REPRESENTATION OR ENDORSEMENT OF SUCH PRODUCTS OR SERVICES, EITHER
ALONE OR IN COMBINATION WITH ANY TI PRODUCT OR SERVICE.
13.2 Community Resources
The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective
contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of
Use.
TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration
among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help
solve problems with fellow engineers.
Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and
contact information for technical support.
13.3 Trademarks
E2E is a trademark of Texas Instruments.
X2Y is a registered trademark of X2Y ATTENUATORS, LLC .
All other trademarks are the property of their respective owners.
13.4 Electrostatic Discharge Caution
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
13.5 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
14 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
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PACKAGE OPTION ADDENDUM
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14-Oct-2022
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
Samples
(4/5)
(6)
VCA822ID
ACTIVE
SOIC
D
14
50
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
VCA822ID
Samples
VCA822IDGST
ACTIVE
VSSOP
DGS
10
250
RoHS & Green
NIPDAUAG
Level-2-260C-1 YEAR
-40 to 85
BOS
Samples
VCA822IDR
ACTIVE
SOIC
D
14
2500
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
VCA822ID
Samples
VCA822IDRG4
ACTIVE
SOIC
D
14
2500
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
VCA822ID
Samples
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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