AD AD828 Dual, low power video op amp Datasheet

a
Dual, Low Power
Video Op Amp
AD828
FUNCTIONAL BLOCK DIAGRAM
FEATURES
Excellent Video Performance
Differential Gain & Phase Error of 0.01% & 0.05
High Speed
130 MHz 3 dB Bandwidth (G = +2)
450 V/s Slew Rate
80 ns Settling Time to 0.01%
Low Power
15 mA Max Power Supply Current
High Output Drive Capability:
50 mA Minimum Output Current per Amplifier
Ideal for Driving Back Terminated Cables
Flexible Power Supply
Specified for +5 V, 5 V and 15 V Operation
3.2 V Min Output Swing into a 150 Load
(VS = 5 V)
Excellent DC Performance
2.0 mV Input Offset Voltage
Available in 8-Lead SOIC and 8-Lead Plastic Mini-DIP
The AD828 is a low cost, dual video op amp optimized for use
in video applications which require gains of +2 or greater and
high output drive capability, such as cable driving. Due to its
low power and single supply functionality, along with excellent
differential gain and phase errors, the AD828 is ideal for power
sensitive applications such as video cameras and professional
video equipment.
With video specs like 0.1 dB flatness to 40 MHz and low differential gain and phase errors of 0.01% and 0.05°, along with
50 mA of output current per amplifier, the AD828 is an excellent choice for any video application. The 130 MHz gain
bandwidth and 450 V/µs slew rate make the AD828 useful in
many high speed applications including: video monitors, CATV,
color copiers, image scanners and fax machines.
V
1
8
V+
–IN1
2
7
OUT2
+IN1
3
6
–IN2
V–
4
5
+IN2
AD828
The AD828 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 15 mA and excellent ac characteristics under all power supply
conditions, make the AD828 the ideal choice for many demanding yet power sensitive applications.
The AD828 is a voltage feedback op amp which excels as a gain
stage (gains >+2) or active filter in high speed and video systems
and achieves a settling time of 45 ns to 0.1%, with a low input
offset voltage of 2 mV max.
The AD828 is available in low cost, small 8-lead plastic miniDIP and SOIC packages.
0.03
0.1F
0.02
VIN
RT
75
RBT
75
1/2
AD828
0.1F
75
RT
75
–V
1k
1k
Figure 1. Video Line Driver
REV. B
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
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
DIFFERENTIAL PHASE – Degrees
DIFF GAIN
0.01
0.07
0.06
DIFFERENTIAL GAIN – Percent
PRODUCT DESCRIPTION
OUT1
DIFF PHASE
0.05
0.04
5
10
SUPPLY VOLTAGE – Volts
15
Figure 2. Differential Phase vs. Supply Voltage
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
World Wide Web Site: http://www.analog.com
Fax: 781/326-8703
© Analog Devices, Inc., 2000
AD828–SPECIFICATIONS (@ T = +25C, unless otherwise noted)
A
Parameter
Conditions
VS
Min
AD828
Typ
DYNAMIC PERFORMANCE
–3 dB Bandwidth
Gain = +2
±5 V
± 15 V
0, +5 V
±5 V
± 15 V
0, +5 V
±5 V
± 15 V
0, +5 V
±5 V
± 15 V
0, +5 V
60
100
30
35
60
20
30
30
10
15
30
10
85
130
45
55
90
35
43
40
18
25
50
19
MHz
MHz
MHz
MHz
MHz
MHz
MHz
MHz
MHz
MHz
MHz
MHz
22.3
MHz
7.2
350
450
250
45
45
80
80
MHz
V/µs
V/µs
V/µs
ns
ns
ns
ns
± 15 V
± 5 V, ± 15 V
± 5 V, ± 15 V
± 15 V
±5 V
0, +5 V
± 15 V
±5 V
0, +5 V
–78
10
1.5
0.01
0.02
0.08
0.05
0.07
0.1
dB
nV/√Hz
pA/√Hz
%
%
%
Degrees
Degrees
Degrees
± 5 V, ± 15 V
0.5
± 5 V, ± 15 V
10
3.3
± 5 V, ± 15 V
25
Gain = –1
Bandwidth for 0.1 dB Flatness
Gain = +2
CC = 1 pF
Gain = –1
CC = 1 pF
Full Power Bandwidth1
Slew Rate
Settling Time to 0.1%
Settling Time to 0.01%
NOISE/HARMONIC PERFORMANCE
Total Harmonic Distortion
Input Voltage Noise
Input Current Noise
Differential Gain Error
(RL = 150 Ω)
Differential Phase Error
(RL = 150 Ω)
VOUT = 5 V p-p
RLOAD = 500 Ω
VOUT = 20 V p-p
RLOAD = 1 kΩ
RLOAD 1 kΩ
Gain = –1
±5 V
–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
f = 10 kHz
f = 10 kHz
NTSC
Gain = +2
NTSC
Gain = +2
DC PERFORMANCE
Input Offset Voltage
± 15 V
±5 V
± 15 V
0, +5 V
±5 V
± 15 V
±5 V
± 15 V
300
400
200
TMIN to TMAX
Offset Drift
Input Bias Current
TMIN
TMAX
Input Offset Current
TMIN to TMAX
Offset Current Drift
Open Loop Gain
VOUT = ± 2.5 V
RLOAD = 500 Ω
TMIN to TMAX
RLOAD = 150 Ω
VOUT = ± 10 V
RLOAD = 1 kΩ
TMIN to TMAX
VOUT = ± 7.5 V
RLOAD = 150 Ω (50 mA Output)
INPUT CHARACTERISTICS
Input Resistance
Input Capacitance
Input Common-Mode Voltage Range
± 15 V
± 15 V
±5 V
± 15 V
0, +5 V
Common-Mode Rejection Ratio
VCM = +2.5 V, TMIN to TMAX
VCM = ± 12 V
TMIN to TMAX
–2–
0.3
±5 V
±5 V
± 15 V
± 15 V
Max
0.02
0.03
0.09
0.1
2
3
6.6
10
4.4
300
500
Unit
mV
mV
µV/°C
µA
µA
µA
nA
nA
nA/°C
3
2
2
5
5.5
2.5
9
V/mV
V/mV
3
5
V/mV
+3.8
–2.7
+13
–12
+3.8
+1.2
82
86
84
300
1.5
+4.3
–3.4
+14.3
–13.4
+4.3
+0.9
100
120
100
kΩ
pF
V
V
V
V
V
V
dB
dB
dB
4
V/mV
V/mV
V/mV
REV. B
AD828
Parameter
OUTPUT CHARACTERISTICS
Output Voltage Swing
Conditions
VS
Min
Typ
RLOAD = 500 Ω
RLOAD = 150 Ω
RLOAD = 1 kΩ
RLOAD = 500 Ω
±5 V
±5 V
± 15 V
± 15 V
3.8
3.6
13.7
13.4
±V
±V
±V
±V
RLOAD = 500 Ω
0, +5 V
± 15 V
±5 V
0, +5 V
± 15 V
3.3
3.2
13.3
12.8
+1.5,
+3.5
50
40
30
90
8
±V
mA
mA
mA
mA
Ω
dB
dB
V/µs
Output Current
Short-Circuit Current
Output Resistance
MATCHING CHARACTERISTICS
Dynamic
Crosstalk
Gain Flatness Match
Skew Rate Match
DC
Input Offset Voltage Match
Input Bias Current Match
Open-Loop Gain Match
Common-Mode Rejection Ratio Match
Power Supply Rejection Ratio Match
POWER SUPPLY
Operating Range
Open Loop
f = 5 MHz
G = +1, f = 40 MHz
G = –1
± 15 V
± 15 V
± 15 V
–80
0.2
10
TMIN to TMAX
TMIN to TMAX
VO = ±10 V, RL = 1 kΩ, TMIN to TMAX
VCM = ± 12 V, TMIN to TMAX
± 5 V to ± 15 V, TMIN to TMAX
± 5 V, ± 15 V
± 5 V, ± 15 V
± 15 V
± 15 V
0.5
0.06
0.01
100
100
Dual Supply
Single Supply
Power Supply Rejection Ratio
± 2.5
+5
±5 V
±5 V
±5 V
Quiescent Current
TMIN to TMAX
TMIN to TMAX
VS = ± 5 V to ± 15 V, TMIN to TMAX
80
80
14.0
14.0
80
NOTES
1
Full power bandwidth = slew rate/2 π VPEAK.
Specifications subject to change without notice.
Max
Unit
2
0.8
0.15
mV
µA
mV/V
dB
dB
± 18
+36
15
15
15
V
V
mA
mA
mA
dB
90
ORDERING GUIDE
Temperature
Range
Model
Package
Description
AD828AN
–40°C to +85°C
AD828AR
–40°C to +85°C
AD828AR-REEL7 –40°C to +85°C
AD828AR-REEL –40°C to +85°C
ABSOLUTE MAXIMUM RATINGS 1
Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ± 18 V
Internal Power Dissipation2
Plastic DIP (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
Package
Option
8-Lead Plastic DIP N-8
8-Lead Plastic SOIC SO-8
7" Tape & Reel
SO-8
13" Tape & Reel
SO-8
2.0
MAXIMUM POWER DISSIPATION – Watts
TJ = +150C
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 DIP Package: θJA = 100°C/Watt
8-Lead SOIC Package: θJA = 155°C/Watt
8-LEAD MINI-DIP PACKAGE
1.5
1.0
0.5
8-LEAD SOIC PACKAGE
0
–50 –40 –30 –20 –10 0 10 20 30 40 50 60 70
AMBIENT TEMPERATURE – C
80
90
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 AD828 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.
REV. B
–3–
WARNING!
ESD SENSITIVE DEVICE
AD828–Typical Characteristics
7.7
QUIESCENT SUPPLY CURRENT PER AMP – mA
INPUT COMMON-MODE RANGE – Volts
20
15
+VCM
10
–V CM
5
7.2
+85°C
–40°C
6.2
5.7
0
0
5
10
15
SUPPLY VOLTAGE – Volts
0
20
20
500
15
450
RL = 500
10
15
10
SUPPLY VOLTAGE – Volts
20
RL = 150
5
400
350
0
5
15
10
SUPPLY VOLTAGE – Volts
300
20
0
30
10
15
SUPPLY VOLTAGE – Volts
20
CLOSED-LOOP OUTPUT IMPEDANCE – 100
25
Vs = 15V
20
15
10
Vs = 5V
5
0
10
5
Figure 8. Slew Rate vs. Supply Voltage
Figure 5. Output Voltage Swing vs. Supply Voltage
OUTPUT VOLTAGE SWING – Volts p-p
5
Figure 7. Quiescent Supply Current per Amp vs. Supply
Voltage for Various Temperatures
SLEW RATE – V/s
OUTPUT VOLTAGE SWING – Volts
Figure 4. Common-Mode Voltage Range vs. Supply
Voltage
0
+25°C
6.7
100
1k
LOAD RESISTANCE – 10k
10
1
0.1
0.01
1k
10k
100k
1M
FREQUENCY – Hz
10M
100M
Figure 9. Closed-Loop Output Impedance vs. Frequency
Figure 6. Output Voltage Swing vs. Load Resistance
–4–
REV. B
100
6
80
PHASE 5V OR
15V SUPPLIES
+100
+80
15V SUPPLIES
5
4
3
60
+60
40
+40
5V SUPPLIES
20
+20
0
2
PHASE MARGIN – Degrees
7
OPEN-LOOP GAIN – dB
INPUT BIAS CURRENT – A
AD828
0
RL = 1k
1
–60
–40
–20
0
20
40
60
80
100
120
–20
1k
140
10k
TEMPERATURE – C
Figure 10. Input Bias Current vs. Temperature
100k
1M
10M
FREQUENCY – Hz
100M
1G
Figure 13. Open-Loop Gain and Phase Margin vs.
Frequency
9
130
110
OPEN-LOOP GAIN – V/mV
SHORT CIRCUIT CURRENT – mA
15V
8
SOURCE CURRENT
90
SINK CURRENT
70
50
30
–60
7
5V
6
5
4
–40
–20
0
20
40
60
80
100
120
3
100
140
1k
LOAD RESISTANCE – TEMPERATURE – C
Figure 14. Open-Loop Gain vs. Load Resistance
Figure 11. Short Circuit Current vs. Temperature
80
10k
100
80
80
70
PHASE MARGIN
60
60
GAIN BANDWIDTH
50
50
+SUPPLY
70
PSR – dB
70
–3dB BANDWIDTH – MHz
PHASE MARGIN – Degrees
90
60
50
–SUPPLY
40
30
20
40
–60
–40
–20
0
20
40
60
80
TEMPERATURE – C
100
120
10
100
40
140
10k
100k
1M
FREQUENCY – Hz
10M
100M
Figure 15. Power Supply Rejection vs. Frequency
Figure 12. –3 dB Bandwidth and Phase Margin vs.
Temperature, Gain = +2
REV. B
1k
–5–
AD828–Typical Characteristics
–40
140
VIN = 1V p-p
GAIN = +2
HARMONIC DISTORTION – dB
–50
CMR – dB
120
100
80
–60
–70
–80
2ND HARMONIC
–90
3RD HARMONIC
–100
100
60
1k
10k
100k
FREQUENCY – Hz
1M
10M
Figure 16. Common-Mode Rejection vs. Frequency
10k
100k
FREQUENCY – Hz
1M
10M
Figure 19. Harmonic Distortion vs. Frequency
30
Hz
50
RL = 1k
INPUT VOLTAGE NOISE – nV/
OUTPUT VOLTAGE – Volts p-p
1k
20
RL = 150
10
0
100k
1M
10M
FREQUENCY – Hz
40
30
20
10
0
100M
0
10
100
1k
10k
FREQUENCY – Hz
100k
10M
1M
Figure 20. Input Voltage Noise Spectral Density vs.
Frequency
Figure 17. Large Signal Frequency Response
10
650
6
550
4
1%
0.1%
SLEW RATE – V/s
OUTPUT SWING FROM 0 TO ±V
8
0.01%
2
0
–2
1%
0.1%
0.01%
–4
450
350
–6
–8
–10
0
20
40
60
80
100
SETTLING TIME – ns
120
140
250
–60
160
–40
–20
0
20
40
60
80
100
120
140
TEMPERATURE – C
Figure 21. Slew Rate vs. Temperature
Figure 18. Output Swing and Error vs. Settling Time
–6–
REV. B
AD828
10
5
6
1k
VIN
GAIN – dB
VOUT
AD828
4
2
1k
VS
15V
5V
+5V
150
1k
3
2
VS
15V
5V
+5V
1k
VOUT
VIN
AD828
0
VS = 15V
1
0
–1
VS = +5V
–4
–2
VS = 5V
VS = 5V
–6
–3
–8
–4
–10
100k
1M
10M
FREQUENCY – Hz
1M
10M
FREQUENCY – Hz
100M
Figure 25. Closed-Loop Gain vs. Frequency, G = –1
DIFF GAIN
0.01
0.06
0.8
0.6
0.4
GAIN – dB
0.02
1.0
DIFFERENTIAL GAIN – Percent
0.03
0.07
VS = +5V
–5
100k
100M
Figure 22. Closed-Loop Gain vs. Frequency
DIFFERENTIAL PHASE – Degrees
FLATNESS
50MHz
25MHz
19MHz
150
VS = 15V
–2
0.1dB
4
FLATNESS
40MHz
43MHz
18MHz
GAIN – dB
8
1pF
0.1dB
1pF
0.2
VS = 15V
0
–0.2
VS = 5V
–0.4
DIFF PHASE
–0.6
0.05
VS = 5V
–0.8
–1.0
100k
0.04
5
15
10
SUPPLY VOLTAGE – Volts
Figure 23. Differential Gain and Phase vs. Supply Voltage
1M
10M
FREQUENCY – Hz
100M
Figure 26. Gain Flatness Matching vs. Supply, G = +2
+5V
–30
0.1F
VOUT
–40
1F
CROSSTALK – dB
–50
3
VIN
–60
5
8
1/2
AD828
1
7
2
–70
1/2
AD828
4
6
RL = 150
0.1F
–80
RL
RL
1F
RL = 1k
–90
–100
–110
10k
–5V
100k
1M
FREQUENCY – Hz
10M
USE GROUND PLANE
PINOUT SHOWN IS FOR MINIDIP PACKAGE
100M
Figure 27. Crosstalk Test Circuit
Figure 24. Crosstalk vs. Frequency
REV. B
–7–
AD828–Typical Characteristics
CF
5V
1k
+VS
50ns
100
3.3F
90
0.01F
HP PULSE (LS)
V
1k
OR FUNCTION IN
(SS)
GENERATOR
50
2
8
1/2
AD828
3
4
VOUT
1
TEKTRONIX
P6201 FET
PROBE
TEKTRONIX
7A24
PREAMP
10
0.01F
0%
RL
5V
3.3F
–VS
Figure 31. Inverter Large Signal Pulse Response ± 15 VS,
CF = 1 pF, RL = 1 kΩ
Figure 28. Inverting Amplifier Connection
2V
50ns
200mV
100
100
90
90
10
10
0%
0%
2V
200mV
Figure 29. Inverter Large Signal Pulse Response ± 5 VS,
CF = 1 pF, RL = 1 kΩ
200mV
10ns
Figure 32. Inverter Small Signal Pulse Response ± 15 VS,
CF = 1 pF, RL= 1500 Ω
10ns
200mV
100
100
90
90
10
10
0%
0%
200mV
10ns
200mV
Figure 30. Inverter Small Signal Pulse Response ± 5 VS,
CF = 1 pF, RL = 150 Ω
Figure 33. Inverter Small Signal Pulse Response ± 5 VS,
CF = 0 pF, RL = 150 Ω
–8–
REV. B
AD828
CF
5V
1k
50ns
1k
100
+VS
90
3.3F
0.01F
2
HP PULSE (LS)
VIN
OR FUNCTION
(SS)
GENERATOR
8
1/2
AD828
100
3
4
VOUT
1
TEKTRONIX
P6201 FET
PROBE
TEKTRONIX
7A24
PREAMP
10
0.01F
50
0%
RL
5V
3.3F
–VS
Figure 37. Noninverting Large Signal Pulse Response
± 15 VS, CF = 1 pF, RL = 1 kΩ
Figure 34. Noninverting Amplifier Connection
1V
50ns
100mV
100
100
90
90
10
10
0%
0%
2V
200mV
Figure 38. Noninverting Small Signal Pulse Response
± 15 VS, CF = 1 pF, RL = 150 Ω
Figure 35. Noninverting Large Signal Pulse Response
± 5 VS, CF = 1 pF, RL = 1 kΩ
100mV
100mV
10ns
100
100
90
90
10
10
0%
0%
200mV
10ns
200mV
Figure 39. Noninverting Small Signal Pulse Response
± 5 VS, CF = 0 pF, RL = 150 Ω
Figure 36. Noninverting Small Signal Pulse Response
± 5 VS, CF = 1 pF, RL = 150 Ω
REV. B
10ns
–9–
AD828
THEORY OF OPERATION
Circuit Board Layout
The AD828 is a low cost, dual video operational amplifier
designed to excel in high performance, high output current video
applications.
Input and output runs should be laid out so as to physically
isolate them from remaining runs. In addition, the feedback
resistor of each amplifier should be placed away from the feedback
resistor of the other amplifier, since this greatly reduces interamp
coupling.
The AD828 (Figure 40) 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 AD828 will drive terminated cables and capacitive loads of
10 pF or less. As the closed-loop gain is increased, the AD828
will drive heavier cap loads without oscillating.
+VS
Choosing Feedback and Gain Resistors
In order to prevent the stray capacitance present at each
amplifier’s summing junction from limiting its performance, the
feedback resistors should be ≤ 1 kΩ. Since the summing junction
capacitance may cause peaking, a small capacitor (1 pF–5 pF)
may be paralleled with Rf to neutralize this effect. Finally, sockets should be avoided, because of their tendency to increase
interlead capacitance.
Power Supply Bypassing
Proper power supply decoupling is critical to preserve the integrity of high frequency signals. In carefully laid out designs,
decoupling capacitors should be placed in close proximity to the
supply pins, while their lead lengths should be kept to a minimum. These measures greatly reduce undesired inductive effects
on the amplifier’s response.
OUTPUT
–IN
Though two 0.1 µF capacitors will typically be effective in decoupling the supplies, several capacitors of different values can
be paralleled to cover a wider frequency range.
+IN
PARALLEL AMPS PROVIDE 100 mA TO LOAD
–VS
Figure 40. AD828 Simplified Schematic
INPUT CONSIDERATIONS
An input protection resistor (RIN in Figure 34) is required in circuits where the input to the AD828 will be subjected to transient
or continuous overload voltages exceeding the ± 6 V maximum
differential limit. This resistor provides protection for the input
transistors by limiting their maximum base current.
By taking advantage of the superior matching characteristics of
the AD828, enhanced performance can easily be achieved by
employing the circuit in Figure 41. Here, two identical cells are
paralleled to obtain even higher load driving capability than that
of a single amplifier (100 mA min guaranteed). R1 and R2 are
included to limit current flow between amplifier outputs that
would arise in the presence of any residual mismatch.
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.
1k
+VS
1F
0.1F
1k
2
R1
5
8
1/2
AD828
1
3
VOUT
VIN
R2
5
5
APPLYING THE AD828
The AD828 is a breakthrough dual amp that delivers precision
and speed at low cost with low power consumption. The AD828
offers excellent static and dynamic matching characteristics,
combined with the ability to drive heavy resistive loads.
As with all high frequency circuits, care should be taken to maintain overall device performance as well as their matching. The
following items are presented as general design considerations.
1/2
AD828
1k
6
4
RL
7
0.1F
1F
1k
–VS
Figure 41. Parallel Amp Configuration
–10–
REV. B
AD828
AIN
3
3
RZ
RZ
1/2
AD828
510
1/2
AD828
1
1
2
2
510
510
510
100FT
RG59A/U
RZ = 75
510
536
536
6
BOUT
BIN
510
7
6
1/2
AD828
1/2
AD828
5
7
AOUT
5
Figure 42. Bidirectional Transmission CKT
Full-Duplex Transmission
Superior load handling capability (50 mA min/amp), high bandwidth, wide supply voltage range and excellent crosstalk
rejection makes the AD828 an ideal choice even for the most
demanding high speed transmission applications.
The schematic below shows a pair of AD828s configured to
drive 100 feet of coaxial cable in a full-duplex fashion.
Two different NTSC video signals are simultaneously applied at
AIN and BIN and are recovered at AOUT and BOUT, respectively.
This situation is illustrated in Figures 43 and 44. These pictures
clearly show that each input signal appears undisturbed at its
output, while the unwanted signal is eliminated at either receiver.
The transmitters operate as followers, while the receivers’ gain is
chosen to take full advantage of the AD828’s unparalleled CMRR.
(In practice this gain is adjusted slightly from its theoretical
value to compensate for cable nonidealities and losses.) RZ is
chosen to match the characteristic impedance of the cable
employed.
Finally, although a coaxial cable was used, the same topology
applies unmodified to a variety of cables (such, as twisted pairs
often used in telephony).
500mV
500mV
100
100
90
AIN
90
BIN
BOUT
AOUT
10
10
0%
0%
500mV
10µs
500mV
10µs
Figure 44. B Transmission/A Reception
Figure 43. A Transmission/B Reception
+15V
A High Performance Video Line Driver
0.1F
The buffer circuit shown in Figure 45 will drive a backterminated 75 Ω video line to standard video levels (1 V p-p)
with 0.1 dB gain flatness to 40 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/amplifier.
VIN
2
RT
75
1.0F
8
1/2
AD828
75
1
RBT
75
3
4
–15V
0.1F
1.0F
1k
1k
Figure 45. Video Line Driver
REV. B
–11–
RT
75
AD828
LOW DISTORTION LINE DRIVER
The AD828 can quickly be turned into a powerful, low distortion line driver (see Figure 46). In this arrangement the AD828
can comfortably drive a 75 Ω back-terminated cable, with a
5 MHz, 2 V p-p input; all of this while achieving the harmonic
distortion performance outlined in the following table.
2nd Harmonic
1. No Load
2. 150 Ω RL Only
3. 150 Ω RL 7.5 Ω RC
–78.5 dBm
–63.8 dBm
–70.4 dBm
+VS
1k
1F
0.1F
3
8
1/2
AD828
1
2
RC
7.5
1k
1k
In this application one half of the AD828 operates at a gain of
2.1 and supplies the current to the load, while the other provides the overall system gain of 2. This is important for two
reasons: the first is to keep the bandwidth of both amplifiers the
same, and the second is to preserve the AD828’s ability to operate from low supply voltage. RC varies with the load and must
be chosen to satisfy the following equation:
6
1/2
VIN
AD828
5
4
75
75
RL
7
75
1F
C1823a–0–6/00 (rev. B) 00879
Configuration
1.1k
0.1F
–VS
RC = MRL,
where M is defined by [(M + 1) GS = GD] and GD = Driver's
Gain, GS = System Gain.
Figure 46. Low Distortion Amplifier
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
8-Lead Plastic Mini-DIP (N) Package
8
5
1
4
PIN 1
0.25
(6.35)
0.1968 (5.00)
0.1890 (4.80)
0.31
(7.87)
0.1574 (4.00)
0.1497 (3.80)
0.30 (7.62)
REF
0.39 (9.91) MAX
0.180.03
(4.570.76)
0.125
(3.18)
MIN
1
4
0.2440 (6.20)
0.2284 (5.80)
0.0196 (0.50)
45
0.0099 (0.25)
0.0098 (0.25)
0.0040 (0.10)
0.0110.003
(0.280.08)
SEATING
PLANE
0.0688 (1.75)
0.0532 (1.35)
0.0192 (0.49)
0.0138 (0.35)
8
0.0098 (0.25) 0 0.0500 (1.27)
0.0160 (0.41)
0.0075 (0.19)
0°
PRINTED IN U.S.A.
SEATING
PLANE
5
0.0500 (1.27)
BSC
15°
0.033
(0.84)
NOM
8
PIN 1
0.0350.01
(0.890.25)
0.1650.01
(4.190.25)
0.0180.003 0.10
(0.460.08) (2.54)
BSC
8-Lead SO (R) Package
–12–
REV. B