AD829

REV. E

–11–

+15V

–15V

COMM

10 F

EACH

AMPLIFIER

10 F

0.1 F

0.1 F

1 F

1 F

0.1 F

0.1 F

PIN 4

PIN 7

INPUT

FREQUENCY

CMRR

100 Hz

1 MHz

10 MHz

64.6dB

44.7dB

23.9dB

AD829

2–8pF

SETTLING TIME

AC CMR ADJUST

3pF

AD829

3pF

1pF

1pF

2k

2k

210

AD848

(G = 5)

A1

A2

A3

200

200

970

50

DC CMR

ADJUST

1k

3pF

2k

(G = 20)

(G = 20)

CIRCUIT GAIN =

+ 1

Figure 38. A High Gain, Video Bandwidth Three Op Amp In Amp Circuit

FREQUENCY – Hz

–47

100M

1M

10M

–44

–41

–38

–35

–32

–29

–26

–23

–20

–17

GAIN = –1

15V

5V

Figure 35. Closed-Loop Frequency Response vs. Supply

for the Inverting Amplifier Using Current Feedback

Compensation

A Low Error Video Line Driver

The buffer circuit shown in Figure 37 will drive a back-termi-

nated 75

Ω video line to standard video levels (1 V p-p) with

0.1 dB gain flatness to 30 MHz with only 0.04

° and 0.02%

differential phase and gain at the 4.43 MHz PAL color

subcarrier frequency. This level of performance, which meets

the requirements for high definition video displays and test

equipment, is achieved using only 5 mA quiescent current.

A High Gain, Video Bandwidth Three Op Amp In Amp

Figure 38 shows a three op amp instrumentation amplifier cir-

cuit which provides a gain of 100 at video bandwidths. At a

circuit gain of 100 the small signal bandwidth equals 18 MHz

into an FET probe. Small signal bandwidth equals 6.6 MHz

with a 50

Ω load. 0.1% settling time is 300 ns.

50

50

COAX

CABLE

0.1 F

3pF

0.1 F

AD829

+15V

–15V

50

50

COAX

CABLE

50

2k

2k

Figure 36. Noninverting Amplifier Connection Using

Current Feedback Compensation

0.1 F

30pF

0.1 F

AD829

+15V

–15V

75

75

COAX

CABLE

75

300

OPTIONAL

2 – 7pF

FLATNESS

TRIM

300

75

Figure 37. A Video Line Driver with a Flatness over

Frequency Adjustment

The input amplifiers operate at a gain of 20, while the output

op amp runs at a gain of 5. In this circuit the main bandwidth

limitation is the gain/ bandwidth product of the output ampli-

fier. Extra care needs to be taken while breadboarding this cir-

cuit, since even a couple of extra picofarads of stray capacitance

at the compensation pins of A1 and A2 will degrade circuit

bandwidth.