AD847

REV. F

–11–

A High Speed, Three Op-Amp In-Amp

The circuit of Figure 26 lends itself well to CCD imaging and

other video speed applications. It uses two high speed CB pro-

cess op-amps: Amplifier A3, the output amplifier, is an AD847.

The input amplifier (A1 and A2) is an AD827, which is a dual

version of the AD847. This circuit has the optional flexibility of

both dc and ac trims for common-mode rejection, plus the abil-

ity to adjust for minimum settling time.

PIN 7 AD847,

PIN 8 AD827

1

µF

1

µF

0.1

µF

0.1

µF

0.1

µF

0.1

µF

EACH

AMPLIFIER

+15V

–15V

COMM

10

µF

10

µF

PIN 4

AD847 & AD827

AD847

2–8pF

SETTLING TIME

AC CMR ADJUST

2k

Ω

1.87k

Ω

2k

Ω

2k

Ω

5pF

200

Ω

DC CMR

ADJUST

2k

Ω

CIRCUIT GAIN =

+ 1

2000

Ω

G

R

IN

+V

2

3

1

A1

1/2

AD827

1k

Ω

–V

IN

6

5

7

A2

1/2

AD827

1k

Ω

2

3

6

A3

100Hz

1kHz

10kHz

100kHz

1MHz

88.3dB

87.4dB

86.2dB

67.4dB

47.1dB

INPUT

FREQUENCY

CMRR

THD + NOISE

BELOW INPUT

LEVEL

@ 10kHz

1

2

10

100

OPEN

2k

Ω

226

Ω

20

Ω

2–8

2–8

2–8

2–8

16.1MHz

14.7MHz

4.5MHz

660kHz

200ns

200ns

370ns

2.5

µs

82dB

82dB

81dB

71dB

GAIN

SMALL

SIGNAL

BANDWIDTH

SETTLING

TIME

TO 0.1%

C

(pF)

ADJ

BANDWIDTH, SETTLING TIME AND TOTAL HARMONIC DISTORTION VS. GAIN

Figure 26. A High Speed In-Amp Circuit for Data Acquisition