AD827

REV. C

–7–

VIDEO LINE DRIVER

The AD827 functions very well as a low cost, high speed line

driver for either terminated or unterminated cables. Figure 23

shows the AD827 driving a doubly terminated cable in a

follower configuration.

0.1 µF

0.1 µF

50

Ω

AD827

1/2

500

Ω

50

Ω

50

Ω

500

Ω

Figure 23. A Video Line Driver

characteristic impedance) minimizes reflections from the far end

of the cable. While operating from

±5 V supplies, the AD827

maintains a typical slew rate of 200 V/

µs, which means it can

drive a

±1 V, 30 MHz signal into a terminated cable.

Table I. Video Line Driver Performance Summary

Over-

shoot

0 dB or

±500 mV Step ±15

20 pF

23 MHz

4%

0 dB or

±500 mV Step ±15

15 pF

21 MHz

0%

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 ±50 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.

impedance of the cable) may be placed between the AD827

output and the cable input, in order to damp any reflected

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

A HIGH SPEED THREE OP AMP INSTRUMENTATION

AMPLIFIER CIRCUIT

The instrumentation amplifier circuit shown in Figure 24 can

provide a range of gains. Table II details performance.

–

+

+

–

+

–

1

3

2

2

3

6

7

6

5

AD847

AD827

AD827

0.1

µF

1k

Ω

2k

Ω

2k

Ω

1k

Ω

2k

Ω

0.1

µF

0.1

µF

2k

Ω

R

L

2 – 8pF

0.1

µF

R

G

4

7

2k

Ω

8

4

TRIM FOR BEST

SETTLING TIME

1/2

1/2

3pF

CIRCUIT GAIN =

+ 1

G

R

2000

TRIM FOR

OPTIMUM

BANDWIDTH

7 – 15 pF

NOTE: PINOUT SHOWN IS FOR MINIDIP PACKAGE

–V

IN

–V

S

+V

IN

+V

S

–V

S

Figure 24. A High Bandwidth Three Op Amp

Instrumentation Amplifier

Table II. Performance Specifications for the

Three Op Amp Instrumentation Amplifier

Small Signal

Bandwidth

Gain

@ 1 V p-p Output

1

Open

16.1 MHz

22 k

14.7 MHz

10

226

Ω

4.9 MHz

100

20

Ω

660 kHz