OP77

Rev. E | Page 10 of 16

TEST CIRCUITS

OP77

200k

Ω

50

Ω

4000

Figure 21. Typical Offset Voltage Test Circuit

INPUT REFERRED NOISE =

25,000

OP77

2.5M

Ω

V+

V–

OUTPUT

100

Ω

100

Ω

3.3k

Ω

4.7µF

(

≈10Hz FILTER)

7

6

4

2

3

Figure 22. Typical Low-Frequency Noise Test Circuit

OP77

V+

OUTPUT

V–

20k

Ω

INPUT

+

–

1

8

7 6

4

2

3

Figure 23. Optional Offset Nulling Circuit

OP77

100k

Ω

+18V

–18V

7

6

4

2

3

+

10µF

+

10µF

0.1µF

0.1µF

*

*

10

Ω

10

Ω

10k

Ω

10k

Ω

NOTES

Figure 24. Burn-In Circuit

1M

Ω

10

Ω

10k

Ω

100k

Ω

TYPICALPRECISION

OP AMP

–10V

0V

+10V

NOTES

1. GAIN NOT CONSISTANT. CAUSES NONLINEAR ERRORS.

3. CHECK SPECIFICATION TABLE 1 AND TABLE 2 FOR PERFORMANCE.

650V/mV

Figure 25. Open-Loop Gain Linearity

Actual open-loop voltage gain can vary greatly at various output

voltages. All automated testers use endpoint testing and therefore

only show the average gain. This causes errors in high closed-

loop gain circuits. Because this is difficult for manufacturers to

test, users should make their own evaluations. This simple test

circuit makes it easy. An ideal op amp would show a horizontal

scope trace.

–10V

0V

+10V

Figure 26. Output Gain Linearity Trace

This is the output gain linearity trace for the new OP77. The

output trace is virtually horizontal at all points, assuring

extremely high gain accuracy. The average open-loop gain is

truly impressive—approximately 10,000,000.