Low Cost, Low Power
Video Op Amp
AD818
FEATURES
Low Cost
Excellent Video Performance
55 MHz 0.1 dB Bandwidth (Gain = +2)
0.01% and 0.05ⴗ Differential Gain and Phase Errors
High Speed
130 MHz Bandwidth (3 dB, G = +2)
100 MHz Bandwidth (3 dB, G+ = –1)
500 V/s Slew Rate
80 ns Settling Time to 0.01% (VO = 10 V Step)
High Output Drive Capability
50 mA Minimum Output Current
Ideal for Driving Back Terminated Cables
Flexible Power Supply
Specified for Single (+5 V) and Dual (ⴞ5 V to ⴞ15 V)
Power Supplies
Low Power: 7.5 mA Max Supply Current
Available in 8-Lead SOIC and 8-Lead PDIP
GENERAL DESCRIPTION
The AD818 is a low cost video op amp optimized for use in
video applications that require gains equal to or greater than +2
or –1. The AD818’s low differential gain and phase errors,
single supply functionality, low power, and high output drive
make it ideal for cable driving applications such as video
cameras and professional video equipment.
With video specs like 0.1 dB flatness to 55 MHz and low differential gain and phase errors of 0.01% and 0.05∞, along with
50 mA of output current, the AD818 is an excellent choice for
CONNECTION DIAGRAM
8-Lead Plastic Mini-DIP (N) and SOIC (R) Packages
NULL
1
–IN
8
NULL
2
7
+VS
+IN
3
6
OUTPUT
–VS
4
5
NC
AD818
TOP VIEW
NC = NO CONNECT
any video application. The 130 MHz 3 dB bandwidth (G = +2)
and 500 V/ms slew rate make the AD818 useful in many high speed
applications including video monitors, CATV, color copiers,
image scanners, and fax machines.
The AD818 is fully specified for operation with a single +5 V
power supply and with dual supplies from ± 5 V to ± 15 V. This
power supply flexibility, coupled with a very low supply current
of 7.5 mA and excellent ac characteristics under all power supply conditions, make the AD818 the ideal choice for many
demanding yet power sensitive applications.
The AD818 is a voltage feedback op amp and excels as a gain
stage in high speed and video systems (gain ≥ 2, or gain £ –1). It
achieves a settling time of 45 ns to 0.1%, with a low input offset
voltage of 2 mV max.
+15V
0.01F
0.02
2.2F
DIFF GAIN
0.01
AD818
75⍀
RT
75⍀
0.1F
2.2F
–15V
1k⍀
1k⍀
DIFFERENTIAL PHASE (Degrees)
RBT
75⍀
VIN
0.00
0.06
DIFFERENTIAL GAIN (%)
The AD818 is available in low cost, small 8-lead PDIP and
SOIC packages.
0.05
DIFF PHASE
0.04
0.03
5
10
SUPPLY VOLTAGE (ⴞV)
15
Figure 1. Video Line Driver
Figure 2. Differential Gain and Phase vs. Supply
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties that
may result from its use. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices. Trademarks and
registered trademarks are the property of their respective companies.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
www.analog.com
Fax: 781.461-3113
©2010 Analog Devices, Inc. All rights reserved.
REV. D
AD818–SPECIFICATIONS
(@ TA = 25ⴗC, unless otherwise noted.)
Parameter
Conditions
VS
Min
DYNAMIC PERFORMANCE
–3 dB Bandwidth
Gain = +2
±5 V
± 15 V
0 V, +5 V
±5 V
± 15 V
0 V, +5 V
±5 V
± 15 V
0 V, +5 V
±5 V
± 15 V
0 V, +5 V
70
100
40
50
70
30
20
40
10
18
40
10
Gain = –1
Bandwidth for 0.1 dB Flatness
Gain = +2
CC = 2 pF
Gain = –1
CC = 2 pF
Full Power Bandwidth*
Slew Rate
Settling Time to 0.1%
VOUT = 5 V p-p
RLOAD = 500 W
VOUT = 20 V p-p
RLOAD = 1 kW
RLOAD = 1 kW
Gain = –1
Total Harmonic Distortion
Differential Gain Error
(RL = 150 W)
–2.5 V to +2.5 V
0 V–10 V Step, AV = –1
–2.5 V to +2.5 V
0 V–10 V Step, AV = –1
FC = 1 MHz
NTSC
Gain = +2
Differential Phase Error
(RL = 150 W)
NTSC
Gain = +2
Settling Time to 0.01%
±5 V
± 15 V
±5 V
± 15 V
0 V, +5 V
±5 V
± 15 V
±5 V
± 15 V
± 15 V
± 15 V
±5 V
0 V, +5 V
± 15 V
±5 V
0 V, +5 V
350
450
250
Cap Load Drive
± 5 V to ± 15 V
INPUT OFFSET VOLTAGE
AD818A
Typ
MHz
MHz
MHz
MHz
MHz
MHz
MHz
MHz
MHz
MHz
MHz
MHz
25.5
MHz
8.0
400
500
300
45
45
80
80
63
0.005
0.01
0.08
0.045
0.06
0.1
10
MHz
V/ms
V/ms
V/ms
ns
ns
ns
ns
dB
%
%
%
Degrees
Degrees
Degrees
pF
0.5
INPUT OFFSET CURRENT
2
3
mV
mV
mV/∞C
3.3
6.6
10
4.4
mA
mA
mA
± 5 V, ± 15 V
25
300
500
nA
nA
nA/∞C
TMIN to TMAX
Offset Current Drift
COMMON-MODE REJECTION
0.09
0.09
± 5 V, ± 15 V
TMIN
TMAX
OPEN-LOOP GAIN
0.01
0.02
10
INPUT BIAS CURRENT
Unit
95
130
55
70
100
50
43
55
18
34
72
19
TMIN to TMAX
Offset Drift
Max
0.3
VOUT = ± 2.5 V
RLOAD = 500 W
TMIN to TMAX
RLOAD = 150 W
VOUT = ± 10 V
RLOAD = 1 kW
TMIN to TMAX
VOUT = ± 7.5 V
RLOAD = 150 W
(50 mA Output)
±5 V
VCM = ± 2.5 V
VCM = ± 12 V
TMIN to TMAX
±5 V
± 15 V
± 15 V
± 15 V
± 15 V
–2–
3
2
2
5
6
3
9
V/mV
V/mV
3
5
V/mV
82
86
84
100
120
100
dB
dB
dB
4
V/mV
V/mV
V/mV
REV. D
AD818
Parameter
Conditions
POWER SUPPLY REJECTION
VS = ± 5 V to ± 15 V
TMIN to TMAX
INPUT VOLTAGE NOISE
f = 10 kHz
INPUT CURRENT NOISE
f = 10 kHz
VS
Min
Max
Unit
90
dB
dB
± 5 V, ± 15 V
10
nV/÷Hz
± 5 V, ± 15 V
1.5
pA/÷Hz
+3.8
–2.7
+13
–12
+3.8
+1.2
+4.3
–3.4
+14.3
–13.4
+4.3
+0.9
V
V
V
V
V
V
3.3
3.2
13.3
12.8
1.5, 3.5
50
50
30
3.8
3.6
13.7
13.4
90
±V
±V
±V
±V
V
mA
mA
mA
mA
INPUT RESISTANCE
300
kW
INPUT CAPACITANCE
1.5
pF
8
W
INPUT COMMON-MODE
VOLTAGE RANGE
80
80
AD818A
Typ
±5 V
± 15 V
0 V, +5 V
OUTPUT VOLTAGE SWING
RLOAD = 500 W
RLOAD = 150 W
RLOAD = 1 kW
RLOAD = 500 W
RLOAD = 500 W
Output Current
Short-Circuit Current
OUTPUT RESISTANCE
POWER SUPPLY
Operating Range
±5 V
±5 V
± 15 V
± 15 V
0 V, +5 V
± 15 V
±5 V
0 V, +5 V
± 15 V
Open Loop
Dual Supply
Single Supply
Quiescent Current
TMIN to TMAX
TMIN to TMAX
±5 V
±5 V
± 15 V
± 15 V
*Full power bandwidth = slew rate/(2p VPEAK).
Specifications subject to change without notice.
REV. D
–3–
± 2.5
+5
7.0
7.0
± 18
+36
7.5
7.5
7.5
7.5
V
V
mA
mA
mA
mA
AD818
ABSOLUTE MAXIMUM RATINGS 1
2.0
TJ = 150 C
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ± 18 V
Internal Power Dissipation2
Plastic (N) . . . . . . . . . . . . . . . . . . . . . . See Derating Curves
Small Outline (R) . . . . . . . . . . . . . . . . . See Derating Curves
Input Voltage (Common Mode) . . . . . . . . . . . . . . . . . . . . ± VS
Differential Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . ± 6 V
Output Short-Circuit Duration . . . . . . . . See Derating Curves
Storage Temperature Range (N, R) . . . . . . . . –65∞C to +125∞C
Operating Temperature Range . . . . . . . . . . . . –40∞C to +85∞C
Lead Temperature Range (Soldering 10 sec) . . . . . . . . . 300∞C
MAXIMUM POWER DISSIPATION (W)
8-LEAD MINI-DIP PACKAGE
NOTES
1
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.
2
Specification is for device in free air: 8-lead plastic package, JA = 90∞C/W; 8-lead
SOIC package, JA = 155∞C/W.
1.5
1.0
0.5
8-LEAD SOIC PACKAGE
0
–50 –40 –30 –20 –10
10
0
20
30
40
50 60 70
80
90
AMBIENT TEMPERATURE (ⴗC)
Figure 3. Maximum Power Dissipation vs. Temperature
for Different Package Types
CAUTION
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily
accumulate on the human body and test equipment and can discharge without detection. Although the
AD818 features proprietary ESD protection circuitry, permanent damage may occur on devices
subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended
to avoid performance degradation or loss of functionality.
METALLIZATION PHOTOGRAPH
Dimensions shown in inches and (mm)
OFFSET OFFSET
NULL
NULL
1
8
+VS
7
–INPUT 2
0.0523
(1.33)
6 OUTPUT
+INPUT 3
4
–VS
0.0559 (1.42)
–4–
REV. D
Typical Performance Characteristics–AD818
20
OUTPUT VOLTAGE SWING (ⴞV)
INPUT COMMON-MODE RANGE (ⴞV)
20
15
+VCM
10
–VCM
5
0
15
RL = 500⍀
10
RL = 150⍀
5
0
0
5
10
15
20
0
5
SUPPLY VOLTAGE (ⴞV)
TPC 1. Common-Mode Voltage Range vs. Supply
8.0
QUIESCENT SUPPLY CURRENT (mA)
OUTPUT VOLTAGE SWING (V p-p)
25
VS = ⴞ15V
20
15
10
VS = ⴞ5V
5
0
10
7.5
+85ⴗC
+25ⴗC
7.0
–40ⴗC
6.5
6.0
100
1k
LOAD RESISTANCE (⍀)
10k
0
5
10
15
20
SUPPLY VOLTAGE (ⴞV)
TPC 2. Output Voltage Swing vs. Load Resistance
TPC 5. Quiescent Supply Current vs. Supply Voltage
600
CLOSED-LOOP OUTPUT IMPEDANCE (⍀)
100
500
SLEW RATE (V/s)
20
15
TPC 4. Output Voltage Swing vs. Supply
30
400
300
200
0
5
10
15
10
1
0.1
0.01
1k
20
SUPPLY VOLTAGE (ⴞV)
10k
100k
1M
10M
100M
FREQUENCY (Hz)
TPC 3. Slew Rate vs. Supply Voltage
REV. D
10
SUPPLY VOLTAGE (ⴞV)
TPC 6. Closed-Loop Output Impedance vs. Frequency
–5–
AD818
7
130
SHORT CIRCUIT CURRENT (mA)
5
4
3
2
1
–60
–40
–20
0
20
40
60
TEMPERATURE (ⴗC)
80
100
120
SOURCE CURRENT
90
SINK CURRENT
70
50
30
–60
140
–40
–20
0
20
40
60
80
100
70
140
TPC 10. Short-Circuit Current vs. Temperature
100
100
95
PHASE ⴞ5V OR
ⴞ15V SUPPLIES
80
80
50
75
GAIN/BANDWIDTH
40
65
–3dB BANDWIDTH (MHz)
85
OPEN-LOOP GAIN (dB)
PHASE MARGIN
60
ⴞ15V SUPPLIES
RL = 1k⍀
60
60
40
40
ⴞ5V SUPPLIES
RL = 1k⍀
20
20
0
0
30
–60
120
TEMPERATURE (ⴗC)
TPC 7. Input Bias Current vs. Temperature
–20
55
140
TEMPERATURE (ⴗC)
100k
1M
10M
FREQUENCY (Hz)
TPC 8. –3 dB Bandwidth and Phase Margin vs.
Temperature, Gain = +2
TPC 11. Open-Loop Gain and Phase Margin vs.
Frequency
–40
–20
0
20
40
60
80
100
120
1k
8
10k
100M
1G
100
9
90
ⴞ15V
80
+SUPPLY
7
70
ⴞ5V
PSR (dB)
OPEN-LOOP GAIN (V/mV)
PHASE MARGIN (Degrees)
110
PHASE MARGIN (Degrees)
INPUT BIAS CURRENT (A)
6
6
60
–SUPPLY
50
40
5
30
4
20
3
100
1k
10
100
10k
LOAD RESISTANCE (⍀)
1k
10k
100k
1M
FREQUENCY (Hz)
10M
100M
TPC 12. Power Supply Rejection vs. Frequency
TPC 9. Open-Loop Gain vs. Load Resistance
–6–
REV. D
AD818
30
120
OUTPUT VOLTAGE (V p-p)
RL = 1k⍀
CMR (dB)
100
80
60
10k
100k
FREQUENCY (Hz)
10M
1M
RL = 150⍀
10
0
100k
40
1k
20
TPC 13. Common-Mode Rejection vs. Frequency
1M
100M
TPC 16. Output Voltage vs. Frequency
10
–40
RL = 150⍀
2V p-p
8
–50
6
HARMONIC DISTORTION (dB)
OUTPUT SWING FROM 0 TO ⴞV (V)
10M
FREQUENCY (Hz)
4
1%
0.1%
0.01%
2
0
–2
1%
0.01%
0.1%
–4
–6
–60
–70
SECOND HARMONIC
–80
THIRD HARMONIC
–90
–8
–10
0
20
40
60
80
100
SETTLING TIME (ns)
120
140
–100
100
160
10k
100k
1M
10M
FREQUENCY (Hz)
TPC 14. Output Swing and Error vs. Settling Time
TPC 17. Harmonic Distortion vs. Frequency
50
650
40
550
SLEW RATE (V/s)
INPUT VOLTAGE NOISE (nV/ Hz)
1k
30
20
350
10
0
1
10
100
1k
10k
FREQUENCY (Hz)
100k
1M
250
–60
10M
TPC 15. Input Voltage Noise Spectral Density vs.
Frequency
REV. D
450
–40
–20
0
20
40
60
80
TEMPERATURE (ⴗC)
100
120
TPC 18. Slew Rate vs. Temperature
–7–
140
AD818
CF
0.02
1k⍀
0.01
+VS
3.3F
0.00
0.06
0.05
DIFF PHASE
0.04
DIFFERENTIAL GAIN (%)
DIFFERENTIAL PHASE (Degrees)
DIFF GAIN
0.01F
HP
VIN 1k⍀
PULSE (LS)
OR FUNCTION
(SS)
GENERATOR
50⍀
AD818
VOUT
TEKTRONIX
P6201 FET
PROBE
TEKTRONIX
7A24
PREAMP
0.01F
RL
0.03
5
10
SUPPLY VOLTAGE (ⴞV)
15
3.3F
–VS
TPC 19. Differential Gain and Phase vs. Supply Voltage
10
VS
CC
0.1dB
FLATNESS
2V
ⴞ15V 2pF 55MHz
ⴞ5V 1pF 43MHz
+5V 1pF 18MHz
9
8
GAIN (dB)
CC
TPC 22. Inverting Amplifier Connection
1k⍀
1k⍀
VOUT
100
90
AD818
VIN
50ns
150⍀
7
6
5
ⴞ15V
ⴞ5V
4
10
3
0%
+5V
2
2V
1
1M
10M
100M
FREQUENCY (Hz)
1G
TPC 20. Closed-Loop Gain vs. Frequency (G = +2)
TPC 23. Inverter Large Signal Pulse Response;
VS = ± 5 V, CF = 1 pF, RL = 1 kW
10
8
6
4
VS
0.1dB
FLATNESS
ⴞ15V
ⴞ5V
+5V
72MHz
34MHz
19MHz
2pF
200mV
1k⍀
1k⍀
VIN
GAIN (dB)
100
90
VOUT
AD818
2
10ns
150⍀
0
–2
ⴞ15V
+5V
–4
10
–6
0%
ⴞ5V
–8
200mV
–10
1M
10M
100M
FREQUENCY (Hz)
1G
TPC 24. Inverter Small Signal Pulse Response;
VS = ± 5 V, CF = 1 pF, RL = 150 W
TPC 21. Closed-Loop Gain vs. Frequency (G = –1)
–8–
REV. D
AD818
CF
1k⍀
5V
50ns
1k⍀
+VS
3.3F
100
90
0.01F
HP
VIN 100⍀
PULSE (LS)
OR FUNCTION
(SS)
GENERATOR
50⍀
10
0%
AD818
VOUT
TEKTRONIX
P6201 FET
PROBE
TEKTRONIX
7A24
PREAMP
0.01F
5V
RL
3.3F
–VS
TPC 25. Inverter Large Signal Pulse Response;
VS = ± 15 V, CF = 1 pF, RL = 1 kW
200mV
TPC 28. Noninverting Amplifier Connection
10ns
1V
100
100
90
90
10
10
0%
0%
200mV
2V
TPC 26. Inverter Small Signal Pulse Response;
VS = ± 15 V, CF = 1 pF, RL = 150 W
200mV
TPC 29. Noninverting Large Signal Pulse Response;
VS = ± 5 V, CF = 1 pF, RL = 1 kW
10ns
100mV
100
10ns
100
90
90
10
10
0%
0%
200mV
200mV
TPC 27. Inverter Small Signal Pulse Response;
VS = ± 5 V, CF = 0 pF, RL = 150 W
REV. D
50ns
TPC 30. Noninverting Small Signal Pulse
Response; VS = ± 5 V, CF = 1 pF, RL = 150 W
–9–
AD818
5V
50ns
100mV
100
100
90
90
10
10
0%
0%
5V
200mV
TPC 31. Noninverting Large Signal Pulse Response;
VS = ± 15 V, CF = 1 pF, RL = 1 kW
100mV
10ns
TPC 33. Noninverting Small Signal Pulse Response;
VS = ± 5 V, CF = 0 pF, RL = 150 W
10ns
100
90
10
0%
200mV
TPC 32. Noninverting Small Signal Pulse Response;
VS = ± 15 V, CF = 1 pF, RL = 150 W
–10–
REV. D
AD818
may result in peaking. A small capacitance (1 pF–5 pF) may be
used in parallel with the feedback resistor to neutralize this effect.
+VS
Power supply leads should be bypassed to ground as close as
possible to the amplifier pins. Ceramic disc capacitors of 0.1 mF
are recommended.
OUTPUT
+VS
–IN
AD818
+IN
10k⍀
–VS
NULL 1
VOS ADJUST
–VS
NULL 8
Figure 5. Offset Null Configuration
Figure 4. AD818 Simplified Schematic
OFFSET NULLING
THEORY OF OPERATION
The AD818 is a low cost video operational amplifier designed to
excel in high performance, high output current video applications.
The AD818 (Figure 4) consists of a degenerated NPN differential pair driving matched PNPs in a folded-cascode gain stage.
The output buffer stage employs emitter followers in a class
AB amplifier that delivers the necessary current to the load, while
maintaining low levels of distortion.
The input offset voltage of the AD818 is inherently very low.
However, if additional nulling is required, the circuit shown
in Figure 5 can be used. The null range of the AD818 in this
configuration is ± 10 mV.
SINGLE SUPPLY OPERATION
Another exciting feature of the AD818 is its ability to perform
well in a single supply configuration. The AD818 is ideally
suited for applications that require low power dissipation and
high output current.
The AD818 will drive terminated cables and capacitive loads of
10 pF or less. As the closed-loop gain is increased, the AD818
will drive heavier capacitive loads without oscillating.
Referring to Figure 6, careful consideration should be given to
the proper selection of component values. The choices for this
particular circuit are: R1 + R3储R2 combine with C1 to form a
low frequency corner of approximately 10 kHz. C4 was inserted
in series with R4 to maintain amplifier stability at high frequency.
INPUT CONSIDERATIONS
An input protection resistor (RIN in TPC 28) is required in
circuits where the input to the AD818 will be subjected to transients of continuous overload voltages exceeding the ± 6 V
maximum differential limit. This resistor provides protection for
the input transistors by limiting their maximum base current.
Combining R3 with C2 forms a low-pass filter with a corner
frequency of approximately 500 Hz. This is needed to maintain
amplifier PSRR, since the supply is connected to VIN through
the input divider. The values for R2 and C2 were chosen to
demonstrate the AD818’s exceptional output drive capability.
In this configuration, the output is centered around 2.5 V. In
order to eliminate the static dc current associated with this level,
C3 was inserted in series with R L.
For high performance circuits, it is recommended that a “balancing” resistor be used to reduce the offset errors caused by
bias current flowing through the input and feedback resistors.
The balancing resistor equals the parallel combination of RIN
and RF and thus provides a matched impedance at each input
terminal. The offset voltage error will then be reduced by more
than an order of magnitude.
VS
R3
100⍀
GROUNDING AND BYPASSING
When designing high frequency circuits, some special precautions
are in order. Circuits must be built with short interconnect leads.
When wiring components, care should be taken to provide a low
resistance, low inductance path to ground. Sockets should be
avoided, since their increased interlead capacitance can degrade
circuit bandwidth.
Feedback resistors should be of low enough value (£1 kW) to
ensure that the time constant formed with the inherent stray
capacitance at the amplifier’s summing junction will not limit
performance. This parasitic capacitance, along with the parallel
resistance of RF储RIN, forms a pole in the loop transmission, which
REV. D
–11–
C2
3.3F
R4
1k⍀
1k⍀
3.3F
SELECT C1, R1, R2
FOR DESIRED LOW
FREQUENCY CORNER.
C4
0.001F
0.01F
R1
3.3k⍀
C1
0.01F
AD818
VIN
R2
3.3k⍀
VOUT
C3
0.1F
RL
150⍀
Figure 6. Single-Supply Amplifier Configuration
AD818
2ⴛ
HP2835
ERROR
SIGNAL
OUTPUT
1M⍀
2ⴛ
HP2835
ERROR AMPLIFIER
VERROR OUTPUT ⴛ 10
100⍀
AD829
15pF
SHORT, DIRECT CONNECTION
TO TEKTRONIX TYPE 11402
OSCILLOSCOPE PREAMP
INPUT SECTION
0.47F
0 TO ⴞ10V
POWER
SUPPLY
0.01F
EI&S
DL1A05GM
MERCURY
RELAY
NULL
ADJUST
7, 8
TTL LEVEL
SIGNAL
GENERATOR
50Hz
OUTPUT
1, 14
1k⍀
50⍀
COAX
CABLE
FALSE
SUMMING
NODE
100⍀
+VS
1.9k⍀
NOTE
USE CIRCUIT BOARD
WITH GROUND PLANE
100⍀
5pF–18pF
500⍀
DEVICE
UNDER
TEST
AD818
50⍀
2.2F
2.2F
–VS
1k⍀
500⍀
DIGITAL
GROUND
ANALOG
GROUND
0.01F
0.47F
0.01F
10pF
SCOPE PROBE
CAPACITANCE
TEKTRONIX P6201
FET PROBE TO
TEKTRONIX TYPE 11402
OSCILLOSCOPE
PREAMP INPUT SECTION
–VS
0.01F
+VS
Figure 7. Settling Time Test Circuit
AD818 SETTLING TIME
A High Performance Video Line Driver
Settling time primarily comprises two regions. The first is the slew
time in which the amplifier is overdriven, where the output voltage
rate of change is at its maximum. The second is the linear time
period required for the amplifier to settle to within a specified
percentage of the final value.
The buffer circuit shown in Figure 8 will drive a back-terminated
75 W video line to standard video levels (1 V p-p) with 0.1 dB
gain flatness to 55 MHz with only 0.05∞ and 0.01% differential
phase and gain at the 3.58 MHz NTSC subcarrier frequency.
This level of performance, which meets the requirements for
high definition video displays and test equipment, is achieved
using only 7 mA quiescent current.
Measuring the rapid settling time of the AD818 (45 ns to 0.1%
and 80 ns to 0.01%—10 V step) requires applying an input pulse
with a very fast edge and an extremely flat top. With the AD818
configured in a gain of –1, a clamped false summing junction
responds when the output error is within the sum of two diode
voltages (approximately 1 V). The signal is then amplified 20 times
by a clamped amplifier whose output is connected directly to a
sampling oscilloscope.
+15V
0.01F
2.2F
RBT
75⍀
VIN
RT
75⍀
AD818
75⍀
RT
75⍀
0.01F
2.2F
–15V
1k⍀
1k⍀
Figure 8. Video Line Driver
–12–
REV. D
AD818
DIFFERENTIAL LINE RECEIVER
A HIGH SPEED, 3-OP AMP IN AMP
The differential receiver circuit of Figure 9 is useful for many
applications—from audio to video. It allows extraction of a low
level signal in the presence of common-mode noise, as shown in
Figure 10.
The circuit of Figure 11 uses three high speed op amps: two
AD818s and an AD817. This high speed circuit lends itself well
to CCD imaging and other video speed applications. It has the
optional flexibility of both dc and ac trims for common-mode
rejection, plus the ability to adjust for minimum settling time.
2pF
1k⍀
1k⍀
VB
+15V
+5V
+VS
10F
0.1F
10F
0.1F
EACH AMPLIFIER
PIN 7
EACH
AMPLIFIER
1F
0.1F
2.2F
0.01F
COMMON
AD818
DIFFERENTIAL
INPUT
OUTPUT
VOUT
0.01F
–15V
PIN 4
EACH
AMPLIFIER
–VS
2.2F
–5V
1k⍀
0.1F
1F
–VIN
A1
1k⍀
AD818
VA
2pF–8pF
SETTLING
TIME AC
CMR ADJUST
2pF
1k⍀
1k⍀
Figure 9. Differential Line Receiver
1k⍀
5pF
90
RL
2k⍀
1k⍀
1V
AD818
1k⍀
5pF
100
VOUT
A3
RG
2pF
3pF
20ns
970⍀
A2
50⍀
DC CMR
ADJUST
AD818
VA
+VIN
BANDWIDTH, SETTLING TIME, AND TOTAL HARMONIC DISTORTION VS. GAIN
10
2V
0%
OUTPUT
Figure 10. Performance of Line Receiver, RL = 150 W,
G = +2
REV. D
CADJ
(pF)
GAIN
RG
3
10
100
1k⍀ 2–8
222⍀ 2–8
20⍀ 2–8
SMALL
SIGNAL
BANDWIDTH
SETTLING
TIME
TO 0.1%
THD + NOISE
BELOW INPUT LEVEL
@ 10kHz
14.7MHz
4.5MHz
960kHz
200ns
370ns
2.5s
82dB
81dB
71dB
Figure 11. High Speed 3-Op Amp In Amp
–13–
AD818
OUTLINE DIMENSIONS
0.400 (10.16)
0.365 (9.27)
0.355 (9.02)
8
5
1
4
0.280 (7.11)
0.250 (6.35)
0.240 (6.10)
0.100 (2.54)
BSC
0.325 (8.26)
0.310 (7.87)
0.300 (7.62)
0.060 (1.52)
MAX
0.210 (5.33)
MAX
0.015
(0.38)
MIN
0.150 (3.81)
0.130 (3.30)
0.115 (2.92)
SEATING
PLANE
0.022 (0.56)
0.018 (0.46)
0.014 (0.36)
0.195 (4.95)
0.130 (3.30)
0.115 (2.92)
0.015 (0.38)
GAUGE
PLANE
0.014 (0.36)
0.010 (0.25)
0.008 (0.20)
0.430 (10.92)
MAX
0.005 (0.13)
MIN
0.070 (1.78)
0.060 (1.52)
0.045 (1.14)
070606-A
COMPLIANT TO JEDEC STANDARDS MS-001
CONTROLLING DIMENSIONS ARE IN INCHES; MILLIMETER DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF INCH EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN.
CORNER LEADS MAY BE CONFIGURED AS WHOLE OR HALF LEADS.
Figure 12. 8-Lead Plastic Dual In-Line Package [PDIP]
(N-8)
Dimensions shown in inches and (millimeters)
5.00 (0.1968)
4.80 (0.1890)
1
5
4
1.27 (0.0500)
BSC
0.25 (0.0098)
0.10 (0.0040)
COPLANARITY
0.10
SEATING
PLANE
6.20 (0.2441)
5.80 (0.2284)
1.75 (0.0688)
1.35 (0.0532)
0.51 (0.0201)
0.31 (0.0122)
0.50 (0.0196)
0.25 (0.0099)
45°
8°
0°
0.25 (0.0098)
0.17 (0.0067)
1.27 (0.0500)
0.40 (0.0157)
COMPLIANT TO JEDEC STANDARDS MS-012-AA
CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN.
012407-A
8
4.00 (0.1574)
3.80 (0.1497)
Figure 13. 8-Lead Standard Small Outline Package [SOIC_N]
Narrow Body
(R-8)
Dimensions shown in millimeters and (inches)
–14–
REV. D
AD818
ORDERING GUIDE
Model1
AD818AN
AD818ANZ
AD818AR
AD818ARZ
AD818AR-REEL
AD818ARZ-REEL
AD818AR-REEL7
AD818ARZ-REEL7
AD818AR-EBZ
1
Temperature Range
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
Package Description
8-Lead Plastic PDIP
8-Lead Plastic PDIP
8-Lead SOIC_N
8-Lead SOIC_N
8-Lead SOIC_N, 13’’ Tape and Reel
8-Lead SOIC_N, 13’’ Tape and Reel
8-Lead SOIC_N, 7’’ Tape and Reel
8-Lead SOIC_N, 7’’ Tape and Reel
Evaluation Board for 8-lead SOIC_N
Z = RoHS Compliant Part.
REVISION HISTORY
10/10—Rev. C to Rev. D
Updated Outline Dimensions ....................................................... 14
Changes to Ordering Guide .......................................................... 15
5/03—Rev. B to Rev. C
Renumbered Figures and TPCs ........................................ Universal
Changes to Specifications ................................................................ 2
Changes to Ordering Guide ............................................................ 4
Changes to Figures 9 and 10 ......................................................... 12
Updated Outline Dimensions ....................................................... 14
©2010 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D00872-0-10/10(D)
REV. D
–15–
Package Option
N-8
N-8
R-8
R-8
R-8
R-8
R-8
R-8
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