Datasheet AD827 (Analog Devices) - 8

AD827 VIDEO LINE DRIVER A HIGH SPEED THREE OP AMP INSTRUMENTATION
The AD827 functions very well as a low cost, high speed line
AMPLIFIER CIRCUIT
driver for either terminated or unterminated cables. Figure 23 The instrumentation amplifier circuit shown in Figure 24 can shows the AD827 driving a doubly terminated cable in a provide a range of gains. Table II details performance. follower configuration.
+VS TRIM FOR BEST +VS 0.1
µ
F SETTLING TIME 2 – 8pF –V 0.1 µF IN 3 8 V + IN 1/2 1 2k
Ω
AD827 R 2 BT – 1/2 +VS V 50
Ω
OUT AD827 0.1
µ
F 50
Ω
R 1k
Ω
T 50
Ω
2k
Ω
7 2 500
Ω
0.1 µF TRIM FOR – R 6 G OPTIMUM AD847 BANDWIDTH 3 V + OUT 7 – 15 pF 2k
Ω
4 –V 0.1
µ
F 2k
Ω
S 3pF RL 2k
Ω
1k
Ω
6 – C 1/2 7 –V C 500
Ω
S 5 AD827 +VIN + 4 0.1
µ
F 2000 CIRCUIT GAIN = + 1 RG –V NOTE: PINOUT SHOWN IS FOR MINIDIP PACKAGE S
Figure 23. A Video Line Driver Figure 24. A High Bandwidth Three Op Amp The termination resistor, RT, (when equal to the cable’s Instrumentation Amplifier characteristic impedance) minimizes reflections from the far end of the cable. While operating from ± 5 V supplies, the AD827
Table II. Performance Specifications for the
maintains a typical slew rate of 200 V/µs, which means it can
Three Op Amp Instrumentation Amplifier
drive a ± 1 V, 30 MHz signal into a terminated cable.
Small Signal Table I. Video Line Driver Performance Summary Bandwidth Gain RG @ 1 V p-p Output Over- V
1 Open 16.1 MHz
IN* VSUPPLY CC –3 dB BW shoot
2 2 k 14.7 MHz 0 dB or ± 500 mV Step ± 15 20 pF 23 MHz 4% 10 226 Ω 4.9 MHz 0 dB or ± 500 mV Step ± 15 15 pF 21 MHz 0% 100 20 Ω 660 kHz 0 dB or ± 500 mV Step ± 15 0 pF 13 MHz 0% 0 dB or ± 500 mV Step ± 5 20 pF 18 MHz 2% 0 dB or ± 500 mV Step ± 5 15 pF 16 MHz 0% 0 dB or ± 500 mV Step ± 5 0 pF 11 MHz 0% *–3 dB bandwidth numbers are for the 0 dBm signal input. Overshoot numbers are the percent overshoot of the 1 V step input. A back-termination resistor (RBT, also equal to the characteristic impedance of the cable) may be placed between the AD827 output and the cable input, in order to damp any reflected signals caused by a mismatch between RT and the cable’s characteristic impedance. This will result in a flatter frequency response, although this requires that the op amp supply ± 2 V to the output in order to achieve a ± 1 V swing at resistor RT. REV. C –7– Document Outline FEATURES CONNECTION DIAGRAMS PRODUCT DESCRIPTION APPLICATION HIGHLIGHTS SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS ORDERING GUIDE METALLIZATION PHOTOGRAPH Typical Performance Characteristics INPUT PROTECTION PRECAUTIONS VIDEO LINE DRIVER A HIGH SPEED THREE OP AMP INSTRUMENTATION AMPLIFIER CIRCUIT A TWO-CHIP VOLTAGE-CONTROLLED AMPLIFIER (VCA) WITH EXPONENTIAL RESPONSE Guidelines for Grounding and Bypassing OUTLINE DIMENSIONS Revision History