Single Supply, High Speed,
Rail-to-Rail Output, Triple Op Amp
ADA4855-3
Data Sheet
–IN1
OUT1
–VS
CONNECTION DIAGRAM
16
15 14
13
12 +VS
NC 1
+IN2 2
11 OUT2
ADA4855-3
+IN3
5
6
7
8
–VS
9
–IN3
10 –IN2
PD 4
OUT3
NC 3
+VS
NOTES
1. NC = NO CONNECT.
2. EXPOSED PAD CONNECTED TO –VS.
07685-001
Voltage feedback architecture
Rail-to-rail output swing: 0.1 V to 4.9 V
High speed amplifiers
410 MHz, −3 dB bandwidth, G = 1
210 MHz, −3 dB bandwidth, G = 2
Slew rate: 870 V/µs
53 MHz, 0.1 dB large signal flatness
5.3 ns settling time to 0.1% with 2 V step
High input common-mode voltage range
−VS − 0.2 V to +VS − 1 V
Supply range: 3 V to 5.5 V
Differential gain error: 0.01%
Differential phase error: 0.01°
Low power
7.8 mA/amplifier typical supply current
Power-down feature
Available in 16-lead LFCSP
+IN1
FEATURES
Figure 1.
APPLICATIONS
Professional video
Consumer video
Imaging
Instrumentation
Base stations
Active filters
GENERAL DESCRIPTION
The ADA4855-3 offers a typical low power of 7.8 mA per amplifier
and is capable of delivering up to 57 mA of load current. It also
features a power-down function for power sensitive applications
that reduces the supply current down to 1 mA.
The ADA4855-3 is available in a 16-lead LFCSP and is designed
to work over the extended industrial temperature range of
−40°C to +105°C.
Rev. A
0
G=1
–1
G=2
G=5
–2
–3
–4
–5
–6
1
100
10
FREQUENCY (MHz)
1000
07685-004
The ADA4855-3 (triple) is a single-supply, rail-to-rail output
operational amplifier. It provides excellent high speed performance
with 410 MHz, −3 dB bandwidth and a slew rate of 870 V/µs. It
has a wide input common-mode voltage range that extends from
0.2 V below ground to 1 V below the positive rail.In addition,
the output voltage swings within 100 mV of either supply rail,
making this rail-to-rail operational amplifier easy to use on singlesupply voltages as low as 3.3 V.
NORMALIZED CLOSED-LOOP GAIN (dB)
1
Figure 2. Frequency Response
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Tel: 781.329.4700 ©2008–2013 Analog Devices, Inc. All rights reserved.
Technical Support
www.analog.com
ADA4855-3
Data Sheet
TABLE OF CONTENTS
Features .............................................................................................. 1
Theory of Operation ...................................................................... 14
Applications ....................................................................................... 1
Applications Information .............................................................. 15
Connection Diagram ....................................................................... 1
Gain Configurations .................................................................. 15
General Description ......................................................................... 1
20 MHz Active Low-Pass Filter ................................................ 15
Revision History ............................................................................... 2
RGB Video Driver ...................................................................... 16
Specifications..................................................................................... 3
Driving Multiple Video Loads .................................................. 16
5 V Operation ............................................................................... 3
PD (Power-Down) Pin .............................................................. 16
3.3 V Operation ............................................................................ 4
Single-Supply Operation ........................................................... 17
Absolute Maximum Ratings ............................................................ 5
Power Supply Bypassing ............................................................ 17
Thermal Resistance ...................................................................... 5
Layout .......................................................................................... 17
Maximum Power Dissipation ..................................................... 5
Outline Dimensions ....................................................................... 18
ESD Caution .................................................................................. 5
Ordering Guide .......................................................................... 18
Pin Configuration and Function Descriptions ............................. 6
Typical Performance Characteristics ............................................. 7
Test Circuits ..................................................................................... 13
REVISION HISTORY
2/13—Rev. 0 to Rev. A
Change CP-16-4 Package to CP-26-23, Figure 1 .......................... 1
Change CP-16-4 Package to CP-26-23, Figure 4 .......................... 6
Updated Outline Dimensions ....................................................... 18
Changes to Ordering Guide .......................................................... 18
11/08—Revision 0: Initial Version
Rev. A | Page 2 of 20
Data Sheet
ADA4855-3
SPECIFICATIONS
5 V OPERATION
TA = 25°C, VS = 5 V, G = 1, RL = 150 Ω, unless otherwise noted.
Table 1.
Parameter
DYNAMIC PERFORMANCE
−3 dB Bandwidth
Bandwidth for 0.1 dB Flatness
Slew Rate
Settling Time to 0.1%
NOISE/DISTORTION PERFORMANCE
Harmonic Distortion (HD2/HD3)
Crosstalk, Output to Output
Input Voltage Noise
Input Current Noise
Differential Gain Error
Differential Phase Error
DC PERFORMANCE
Input Offset Voltage
Input Offset Voltage Drift
Input Bias Current
Input Offset Current
Open-Loop Gain
INPUT CHARACTERISTICS
Input Resistance
Input Capacitance
Input Common-Mode Voltage Range
Common-Mode Rejection Ratio
OUTPUT CHARACTERISTICS
Output Voltage Swing
Linear Output Current per Amplifier
POWER-DOWN
Turn-On Time
Turn-Off Time
Bias Current
Turn-On Voltage
POWER SUPPLY
Operating Range
Quiescent Current per Amplifier
Supply Current When Powered Down
Power Supply Rejection Ratio
Test Conditions
Min
Typ
Max
Unit
VO = 0.1 V p-p
VO = 2 V p-p
VO = 0.1 V p-p, G = 2
VO = 2 V p-p, G = 2
VO = 2 V p-p
VO = 2 V p-p, G = 2
VO = 2 V step
VO = 2 V step (rise/fall)
VO = 2 V step (rise/fall), G = 2
410
200
210
120
53
50
870
5.3/9.5
7.4/7
MHz
MHz
MHz
MHz
MHz
MHz
V/µs
ns
ns
fC = 5 MHz, VO = 2 V p-p, RL = 1 kΩ
fC = 20 MHz, VO = 2 V p-p, RL = 1 kΩ
f = 5 MHz, G = 2
f = 100 kHz
f = 100 kHz
G=2
G=2
−84/−105
−60/−66
−90
6.8
2
0.01
0.01
dBc
dBc
dBc
nV/√Hz
pA/√Hz
%
Degrees
VO = 0.5 V to 4.5 V
1.3
5.5
−3.8
±0.05
92
3
6.4
0.5
mV
µV/°C
µA
µA
dB
VCM = –0.2 V to +4 V
94
MΩ
pF
V
dB
HD2 ≤ −60 dBc, RL = 10 Ω
0.1 to 4.9
57
V
mA
78
1.2
0.3
−125
+VS − 1.25
ns
µs
µA
µA
V
−VS − 0.2
On
Off
+VS − 1
3
∆VS = 4.5 V to 5.5 V
Rev. A | Page 3 of 20
5.5
7.8
1.1
96
V
mA
mA
dB
ADA4855-3
Data Sheet
3.3 V OPERATION
TA = 25°C, VS = 3.3 V, G = 1, RL = 150 Ω, unless otherwise noted.
Table 2.
Parameter
DYNAMIC PERFORMANCE
−3 dB Bandwidth
Bandwidth for 0.1 dB Flatness
Slew Rate
Settling Time to 0.1%
NOISE/DISTORTION PERFORMANCE
Harmonic Distortion (HD2/HD3)
Crosstalk, Output to Output
Input Voltage Noise
Input Current Noise
Differential Gain Error
Differential Phase Error
DC PERFORMANCE
Input Offset Voltage
Input Offset Voltage Drift
Input Bias Current
Input Offset Current
Open-Loop Gain
INPUT CHARACTERISTICS
Input Resistance
Input Capacitance
Input Common-Mode Voltage Range
Common-Mode Rejection Ratio
OUTPUT CHARACTERISTICS
Output Voltage Swing
Linear Output Current per Amplifier
POWER-DOWN
Turn-On Time
Turn-Off Time
Turn-On Voltage
POWER SUPPLY
Operating Range
Quiescent Current per Amplifier
Supply Current When Powered Down
Power Supply Rejection Ratio
Test Conditions
Min
Typ
Max
Unit
VO = 0.1 V p-p
VO = 1.4 V p-p
VO = 0.1 V p-p, G = 2
VO = 2 V p-p, G = 2
VO = 1.4 V p-p, G = 2
VO = 2 V step, G = 2
VO = 2 V step (rise/fall), G = 2
430
210
210
125
55
870
7.4/7.1
MHz
MHz
MHz
MHz
MHz
V/µs
ns
fC = 5 MHz, VO = 2 V p-p, RL = 1 kΩ
fC = 20 MHz, VO = 2 V p-p, RL = 1 kΩ
f = 5 MHz, G = 2
f = 100 kHz
f = 100 kHz
G=2
G=2
−76/−76
−68/−75
−88
6.8
2
0.01
0.01
dBc
dBc
dBc
nV/√Hz
pA/√Hz
%
Degrees
VO = 0.5 V to 4.5 V
1.3
5.5
−3.8
0.05
92
mV
µV/°C
µA
µA
dB
6.4
0.5
VCM = –0.2 V to +3.2 V
94
MΩ
pF
V
dB
HD2 ≤ −60 dBc, RL = 10 Ω
0.1 to 3.22
40
V
mA
78
1.2
+VS − 1.25
ns
µs
V
−VS − 0.2
+VS − 1
3
∆VS = 2.97 V to 3.63 V
Rev. A | Page 4 of 20
5.5
7.5
0.95
94
V
mA
mA
dB
Data Sheet
ADA4855-3
ABSOLUTE MAXIMUM RATINGS
MAXIMUM POWER DISSIPATION
1
Rating
6V
See Figure 3
(−VS − 0.2 V) to (+VS − 1 V)
±VS
Observe power curves
−65°C to +125°C
−40°C to +105°C
300°C
Specification is for device in free air.
Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. This is a stress
rating only; functional operation of the device at these or any
other conditions above those indicated in the operational
section of this specification is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect
device reliability.
The maximum power that can be safely dissipated by the
ADA4855-3 is limited by the associated rise in junction
temperature. The maximum safe junction temperature for
plastic encapsulated devices is determined by the glass
transition temperature of the plastic, approximately 150°C.
Temporarily exceeding this limit may cause a shift in parametric
performance due to a change in the stresses exerted on the die
by the package. Exceeding a junction temperature of 175°C for
an extended period can result in device failure.
To ensure proper operation, it is necessary to observe the
maximum power derating curves.
3.0
THERMAL RESISTANCE
θJA is specified for the worst-case conditions, that is, θJA is specified
for a device soldered in a circuit board for surface-mount packages.
2.5
2.0
1.5
1.0
0.5
07685-103
Parameter
Supply Voltage
Internal Power Dissipation1
Common-Mode Input Voltage
Differential Input Voltage
Output Short-Circuit Duration
Storage Temperature Range
Operating Temperature Range
Lead Temperature (Soldering, 10 sec)
MAXIMUM POWER DISSIPATION (W)
Table 3.
90
100
80
60
70
40
50
30
10
20
0
0
Unit
°C/W
–10
θJC
17.5
–20
θJA
67
–40
Package Type
16-Lead LFCSP
–30
Table 4.
AMBIENT TEMPERATURE (°C)
Figure 3. Maximum Power Dissipation vs. Ambient Temperature
ESD CAUTION
Rev. A | Page 5 of 20
ADA4855-3
Data Sheet
+IN1
–IN1
OUT1
–VS
PIN CONFIGURATION AND FUNCTION DESCRIPTIONS
16
15 14
13
12 +VS
NC 1
11 OUT2
ADA4855-3
6
7
+VS
8
–VS
5
OUT3
9
–IN3
10 –IN2
PD 4
+IN3
NC 3
NOTES
1. NC = NO CONNECT.
2. EXPOSED PAD CONNECTED TO –VS.
07685-003
+IN2 2
Figure 4. Pin Configuration
Table 5. Pin Function Descriptions
Pin No.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17 (EPAD)
Mnemonic
NC
+IN2
NC
PD
+IN3
−IN3
OUT3
−VS
+VS
−IN2
OUT2
+VS
−VS
OUT1
−IN1
+IN1
Exposed Pad (EPAD)
Description
No Connect.
Noninverting Input 2.
No Connect.
Power Down.
Noninverting Input 3.
Inverting Input 3.
Output 3.
Negative Supply.
Positive Supply.
Inverting Input 2.
Output 2.
Positive Supply.
Negative Supply.
Output 1.
Inverting Input 1.
Noninverting Input 1.
The exposed pad must be connected to −VS.
Rev. A | Page 6 of 20
Data Sheet
ADA4855-3
TYPICAL PERFORMANCE CHARACTERISTICS
T = 25°C, VS = 5V, G = 1, RF = 1 kΩ for G > 1, RL = 150 Ω, small signal VOUT = 100 mV p-p, and large signal VOUT = 2 V p-p, unless
otherwise noted.
0
G=1
–1
G=2
G=5
–2
–3
–4
–5
–6
100
10
FREQUENCY (MHz)
1
1000
0
G=1
G=2
–1
–2
G=5
–3
–4
–5
–6
Figure 5. Small Signal Frequency Response vs. Gain
1
NORMALIZED CLOSED-LOOP GAIN (dB)
G=1
0
–1
G=5
G=2
–3
–4
–5
0
G=1
VOUT = 1.4V p-p
–1
–2
–3
G=5
VOUT = 2V p-p
–4
–5
VS = 3.3V
VS = 3.3V
1
100
10
FREQUENCY (MHz)
1000
–6
07685-005
–6
1
Figure 6. Small Signal Frequency Response vs. Gain
10
100
FREQUENCY (MHz)
1000
07685-008
–2
G=2
VOUT = 2V p-p
Figure 9. Large Signal Frequency Response vs. Gain
1
1
CF = 4.4pF
RL = 1kΩ
CF = 6.6pF
0
CLOSED-LOOP GAIN (dB)
0
–1
RL = 150Ω
–2
–3
–4
CF = 2.2pF
–1
–2
–3
–4
–5
–5
1
100
10
FREQUENCY (MHz)
1000
–6
07685-006
–6
1
Figure 7. Small Signal Frequency Response vs. Load
10
100
FREQUENCY (MHz)
1000
Figure 10. Small Signal Frequency Response vs. Capacitive Load
Rev. A | Page 7 of 20
07685-009
NORMALIZED CLOSED-LOOP GAIN (dB)
1000
Figure 8. Large Signal Frequency Response vs. Gain
1
CLOSED-LOOP GAIN (dB)
100
10
FREQUENCY (MHz)
1
07685-007
NORMALIZED CLOSED-LOOP GAIN (dB)
1
07685-004
NORMALIZED CLOSED-LOOP GAIN (dB)
1
Data Sheet
0.2
6.2
0.1
6.1
CLOSED-LOOP GAIN (dB)
VS = 3.3V, VOUT = 1.4V p-p
–0.1
VS = 5V, VOUT = 2V p-p
–0.2
–0.3
1
10
100
FREQUENCY (MHz)
5.8
5.7
G=2
5.5
1000
1
10
100
FREQUENCY (MHz)
Figure 11. 0.1 dB Flatness vs. Supply Voltage
1
0
75
–50
PHASE
50
GAIN (dB)
–2
–3
–100
GAIN
25
–150
0
–200
–25
–250
–4
–6
07685-038
–5
1
10
100
FREQUENCY (MHz)
1000
–50
10
100k
1M
10M
100M
1G
–300
10G
–50
VOUT = 1V p-p
VS = 3.3V
RL = 1kΩ
–60
–60
VOUT = 1V p-p
RL = 1kΩ
DISTORTION (dBc)
–70
–65
–70
–75
HD2
–80
HD3
–85
1
FREQUENCY (MHz)
–80
–90
–100
HD2
–110
–120
07685-014
DISTORTION (dBc)
10k
Figure 15. Open-Loop Gain and Phase vs. Frequency
–50
–90
0.1
1k
FREQUENCY (Hz)
Figure 12. Small Signal Frequency Response vs. Temperature
–55
100
10
–130
0.1
40
Figure 13. Harmonic Distortion vs. Frequency
HD3
07685-011
CLOSED-LOOP GAIN (dB)
100
TA = –40°C
TA = +25°C
–1
1000
Figure 14. 0.1 dB Flatness vs. Supply Voltage
TA = +85°C
TA = +105°C
0
07685-040
–0.5
VS = 3.3V
5.9
5.6
07685-037
–0.4
6.0
PHASE (Degrees)
0
VS = 5V
1
FREQUENCY (MHz)
10
Figure 16. Harmonic Distortion vs. Frequency
Rev. A | Page 8 of 20
40
07685-035
CLOSED-LOOP GAIN (dB)
ADA4855-3
Data Sheet
ADA4855-3
–40
0
–50
–60
–40
OUT3
–60
IN2, IN3, OUT1
CROSSTALK (dB)
OUT1
–80
–70
IN1, IN2, OUT3
–80
–90
IN1, IN3, OUT2
–100
OUT2
–110
07685-012
–100
–120
0.1
1
10
FREQUENCY (MHz)
100
07685-015
FORWARD ISOLATION (dB)
–20
–120
1000
Figure 17. Forward Isolation vs. Frequency
1000
100
10
FREQUENCY (MHz)
1
Figure 20. Crosstalk vs. Frequency
0
–30
–10
–40
–20
–50
CMRR (dB)
PSRR (dB)
–30
–40
–PSRR
+PSRR
–50
–60
–70
–60
–70
–80
–80
0.1
1
10
FREQUENCY (MHz)
–100
0.01
100
Figure 18. Power Supply Rejection Ratio (PSRR) vs. Frequency
0.1
1
10
FREQUENCY (MHz)
100
Figure 21. Common-Mode Rejection Ratio (CMRR) vs. Frequency
100
07685-020
10
1
10
100
1k
10k
100k
FREQUENCY (Hz)
1M
VS = 5V
VS = 3.3V
10
07685-017
VOLTAGE NOISE (nV/√Hz)
100
CURRENT NOISE (pA/√Hz)
07685-016
–100
0.01
–90
07685-013
–90
1
10
10M
100
1k
10k
FREQUENCY (Hz)
100k
Figure 22. Input Voltage Noise vs. Frequency
Figure 19. Input Current Noise vs. Frequency
Rev. A | Page 9 of 20
1M
ADA4855-3
0.08
0.06
Data Sheet
1.5
VS = 3.3V
VS = 5V
CL = 2.2pF
CL = 4.4pF
CL = 6.6pF
0.04
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
1.0
0.02
0
–0.02
0.5
0
–0.5
–0.04
07685-018
–1.5
TIME (10ns/DIV)
TIME (10ns/DIV)
Figure 26. Large Signal Transient Response vs. Capacitive Load
0.08
0.08
0.06
0.06
0.02
CL = 2.2pF
CL = 4.4pF
CL = 6.6pF
OUTPUT VOLTAGE (V)
0.04
0
–0.02
0.02
0
–0.02
–0.04
–0.06
–0.06
–0.08
VS = 3.3V
–0.08
TIME (10ns/DIV)
TIME (10ns/DIV)
Figure 27. Small Signal Transient Response vs. Capacitive Load
Figure 24. Small Signal Transient Response vs. Capacitive Load
1.5
CL = 2.2pF
CL = 4.4pF
CL = 6.6pF
0.04
–0.04
07685-019
OUTPUT VOLTAGE (V)
Figure 23. Small Signal Transient Response vs. Supply Voltage
07685-023
–0.08
07685-022
–1.0
–0.06
23.7
RL = 150Ω
RL = 1kΩ
QUIESCENT CURRENT (mA)
0.5
0
–0.5
23.2
22.7
22.2
–1.5
21.7
2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5
TIME (10ns/DIV)
SUPPLY VOLTAGE (V)
Figure 28. Quiescent Current vs. Supply Voltage
Figure 25. Large Signal Transient Response vs. Load Resistance
Rev. A | Page 10 of 20
07685-029
–1.0
07685-021
OUTPUT VOLTAGE (V)
1.0
Data Sheet
ADA4855-3
4
2.5
2 × VIN
2.0
3
2 × VIN
1.5
2
VOUT
VOLTAGE (V)
1
VOLTAGE (V)
VOUT
1.0
0
–1
0.5
0
–0.5
–1.0
–2
–1.5
G=2
–4
–2.0
G=2
VIN = 3.3V
–2.5
TIME (50ns/DIV)
TIME (50ns/DIV)
Figure 29. Output Overdrive Recovery
Figure 32. Output Overdrive Recovery
3
2.0
VOUT = 1V p-p
VS = 3.3V
CL = 2.2pF
CL = 4.4pF
CL = 6.6pF
1.5
OUTPUT VOLTAGE (V)
0.4
VPD
VOUT
0.2
0
–0.2
2
1.0
1
0.5
0
0
–0.5
–1
–1.0
–0.4
POWER-DOWN VOLTAGE (V)
0.6
07685-026
–2
–0.6
TIME (10ns/DIV)
07685-129
OUTPUT VOLTAGE (V)
07685-028
07685-025
–3
–1.5
–3
–2.0
TIME (1µs/DIV)
Figure 30. Large Signal Transient Response vs. Capacitive Load
Figure 33. Turn-On/Turn-Off Time
0.5
0.5
0.4
0.4
0.3
0.3
INPUT
SETTLING TIME (%)
0.1
0
ERROR
–0.1
–0.2
0.2
0.1
0
–0.1
ERROR
–0.2
–0.3
–0.3
–0.4
–0.5
–0.4
07685-027
0.2
07685-024
SETTLING TIME (%)
INPUT
VS = 3.3V
–0.5
TIME (2ns/DIV)
TIME (2ns/DIV)
Figure 34. Settling Time
Figure 31. Settling Time
Rev. A | Page 11 of 20
ADA4855-3
Data Sheet
0
100
OUTPUT IMPEDANCE (Ω)
OFFSET VOLTAGE (mV)
–10
–20
–30
VS = 3.3V
–40
VS = 5V
10
1
0.1
–60
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
COMMON-MODE VOLTAGE (V)
4.5
0.01
0.1
5.0
Figure 35. Input Offset Voltage vs. Common-Mode Voltage
5.00
SATURATION VOLTAGE (mV)
QUIESCENT CURRENT (mA)
4.95
23.2
23.0
22.8
22.6
VS = 3.3V
22.4
22.2
4.90
4.85
4.80
4.75
4.70
4.65
–25
–10
5
20
35
50
65
80
95
110
125
TEMPERATURE (°C)
07685-032
22.0
Figure 36. Quiescent Current vs. Temperature
2.2
2.0
1.8
1.6
1.4
07685-034
1.2
–20
0
20
40
60
TEMPERATURE (°C)
80
4.60
0.01
0.1
1
LOAD CURRENT (mA)
10
Figure 39. Output Saturation Voltage vs. Load Current
2.4
OFFSET VOLTAGE (mV)
1000
VS = 5V
23.4
1.0
–40
10
100
FREQUENCY (MHz)
Figure 38. Output Impedance vs. Frequency
23.6
21.8
–40
1
07685-039
0
07685-036
07685-031
–50
100
Figure 37. Offset Drift vs. Temperature
Rev. A | Page 12 of 20
100
Data Sheet
ADA4855-3
TEST CIRCUITS
+VS
10µF
+VS
+
10µF
+
1kΩ
0.1µF
0.1µF
VIN
VOUT
VIN
RL
49.9Ω
0.1µF
1kΩ
0.1µF
1kΩ
VOUT
53.6Ω
RL
1kΩ
10µF
+
0.1µF
07685-041
0.1µF
–VS
07685-044
+
10µF
–VS
Figure 40. Noninverting Load Configuration
Figure 43. Common-Mode Rejection
+VS
+VS
10µF
+
49.9Ω
AC
0.1µF
VOUT
VOUT
RL
RL
49.9Ω
AC
07685-042
0.1µF
–VS
–VS
Figure 41. Positive Power Supply Rejection
Figure 44. Negative Power Supply Rejection
+VS
+VS
10µF
10µF
+
+
RF
RG
0.1µF
RF
0.1µF
0.1µF
0.1µF
VOUT
VIN
CL
49.9Ω
VOUT
VIN
RL
RL
49.9Ω
10µF
–VS
+
07685-043
+
10µF
0.1µF
0.1µF
–VS
Figure 42. Typical Capacitive Load Configuration
07685-046
RG
07685-045
+
10µF
Figure 45. Typical Noninverting Gain Configuration
Rev. A | Page 13 of 20
ADA4855-3
Data Sheet
THEORY OF OPERATION
Besides a novel input stage, the ADA4855-3 employs the Analog
Devices, Inc., patented rail-to-rail output stage. This output
stage makes efficient use of the power supplies, allowing the
op amp to drive up to three video loads to within 350 mV of
the positive power rail. In addition, this output stage provides
the amplifier with very fast overdrive characteristics, which is
an important property in video applications.
The ADA4855-3 comes in a 16-lead LFCSP that has an exposed
thermal pad for lower operating temperature. This pad is internally
connected to the negative rail. To avoid printed circuit board (PCB)
layout problems, the ADA4855-3 features a new pinout flow
that is optimized for video applications. As shown in Figure 4,
the noninverting input and output pins of each amplifier are
adjacent to each other for ease of layout.
The ADA4855-3 is fabricated in Analog Devices dielectrically
isolated eXtra Fast Complementary Bipolar 3 (XFCB3) process,
which results in the outstanding speed and dynamic range
displayed by the amplifier.
+VS
C1
Gm2
+IN
–IN
R
C
–VS
Figure 46. High Level Design Schematic
Rev. A | Page 14 of 20
OUT
Gm1
07685-147
The ADA4855-3 is a voltage feedback op amp that employs a
new input stage that achieves a high slew rate while maintaining
a wide common-mode input range. The input common-mode
range of the ADA4855-3 extends from 200 mV below the
negative rail to 1 V below the positive rail. This feature makes
the ADA4855-3 ideal for single-supply applications. In addition,
this new input stage does not sacrifice noise performance for
slew rate. At 6.8 nV/√Hz, the ADA4855-3 is one of the lowest
noise rail-to-rail output video amplifiers in the market.
Data Sheet
ADA4855-3
APPLICATIONS INFORMATION
GAIN CONFIGURATIONS
20 MHz ACTIVE LOW-PASS FILTER
The ADA4855-3 is a single-supply, high speed, voltage feedback
amplifier. Table 6 provides a convenient reference for quickly
determining the feedback and gain set resistor values and
bandwidth for common gain configurations.
The ADA4855-3 triple amplifier lends itself to higher order
active filters. Figure 49 shows a 20 MHz, 6-pole, Sallen-Key
low-pass filter.
R7
1kΩ
R8
261Ω
Table 6. Recommended Values and Frequency Performance1
RG
N/A
1 kΩ
200 Ω
–
VIN
R1
232Ω
C1
15pF
C2
6.6pF
Conditions: VS = 5 V, TA = 25°C, RL = 150 Ω.
Figure 47 and Figure 48 show the typical noninverting and
inverting configurations and recommended bypass capacitor values.
+VS
R9
R10
1kΩ
261Ω
–
R3
309Ω
10µF
0.1µF
VIN
OUT1
U1
OP AMP
+
R2
1.69kΩ
C3
15pF
OUT2
U2
OP AMP
+
R4
1.87kΩ
C4
4.3pF
+
ADA4855-3
VOUT
0.1µF
–
R11
R12
1kΩ
261Ω
–
0.1µF
R5
261Ω
10µF
RF
C5
33pF
07685-047
–VS
RG
OUT3
VOUT
C6
3pF
Figure 49. 20 MHz, 6-Pole Low-Pass Filter
Figure 47. Noninverting Gain Configuration
The filter has a gain of approximately 6 dB and flat frequency
response out to 14 MHz. This type of filter is commonly used at
the output of a video DAC as a reconstruction filter. The frequency
response of the filter is shown in Figure 50.
RF
+VS
U3
OP AMP
+
R6
1.43kΩ
07685-049
1
RF
0Ω
1 kΩ
1 kΩ
Large Signal 0.1 dB
Flatness (MHz)
53
50
6
10µF
10
0.1µF
–
OUT2
OUT1
–10
ADA4855-3
MAGNITUDE (dB)
VOUT
0.1µF
+
0.1µF
10µF
–VS
–20
–30
–40
–50
07685-048
VIN
OUT3
0
RG
–60
–70
Figure 48. Inverting Gain Configuration
1
10
FREQUENCY (MHz)
100
Figure 50. 20 MHz, Low-Pass Filter Frequency Response
Rev. A | Page 15 of 20
200
07685-050
Gain
1
2
5
−3 dB SS
BW (MHz)
200
120
45
ADA4855-3
Data Sheet
6.5
RGB VIDEO DRIVER
6.0
Figure 51 shows a typical RGB driver application using dual
supplies. The gain of the amplifier is set at +2, where RF = RG =
1 kΩ. The amplifier inputs are terminated with shunt 75 Ω
resistors, and the outputs have series 75 Ω resistors for proper
video matching. In Figure 51, the PD pin is not shown connected
to any signal source for simplicity. If the power-down function
is not used, it is recommended that the PD pin be tied to the
positive supply or be left floating (not connected).
RL = 150Ω
RL = 75Ω
RL = 50Ω
MAGNITUDE (dB)
5.5
5.0
4.5
4.0
VOUT = 2V p-p
G=2
3.5
75Ω
1kΩ
1kΩ
VIN (R)
75Ω
2.5
VOUT (R)
07685-153
3.0
1
10
FREQUENCY (MHz)
–VS
16
15
14
PD (POWER-DOWN) PIN
13
0.1µF
VIN (G)
75Ω
1
12
2
11
ADA4855-3
3
10
PD 4
9
5
6
7
+VS
75Ω
VOUT (G)
1kΩ 1kΩ
+VS
0.1µF
8
+
10µF
0.1µF
0.1µF
VIN (B)
–VS
75Ω
75Ω
1kΩ
VOUT (B)
07685-051
1kΩ
Figure 51. RGB Video Driver
DRIVING MULTIPLE VIDEO LOADS
Each amplifier in the ADA4855-3 can drive up to three video
loads simultaneously, as shown in Figure 52. When driving
three video loads, the ADA4855-3 maintains its excellent
performance for 0.1 dB flatness and 3 dB bandwidth. Figure 53
shows the large signal frequency response of the ADA4855-3
with three different load configurations: 150 Ω, 75 Ω and 50 Ω.
The ADA4855-3 is equipped with a PD (power-down) pin
for all three amplifiers. This allows the user to reduce the
quiescent supply current when an amplifier is inactive. The
power-down threshold levels are derived from the voltage
applied to the +VS pin. When used in single-supply applications,
this is especially useful with conventional logic levels. The
amplifier is enabled when the voltage applied to the PD pin is
greater than +VS − 1.25 V. In a single-supply application, the
voltage threshold is typically +3.75 V, and in a ±2.5 V dualsupply application, the voltage threshold is typically +1.25 V.
The amplifier is also enabled when the PD pin is left floating (not
connected). However, the amplifier is powered down when the
voltage on the PD pin is lower than 2.5 V from +VS. If the PD
pin is not used, it is best to connect it to the positive supply.
Table 7. Power-Down Voltage Control
PD Pin
5V
±2.5 V
3V
Not Active
Active
>3.75 V
1.25 V
1.75 V
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