OP77

Data Sheet

Rev. G | Page 10 of 16

TEST CIRCUITS

OP77

200kΩ

VO

50Ω

VOS =

VO

4000

Figure 21. Typical Offset Voltage Test Circuit

INPUT REFERRED NOISE =

VO

25,000

OP77

2.5MΩ

V+

V–

OUTPUT

100Ω

100Ω

3.3kΩ

4.7µF

(≈10Hz FILTER)

7

6

4

2

3

Figure 22. Typical Low-Frequency Noise Test Circuit

OP77

V+

OUTPUT

V–

20kΩ

INPUT

+

–

1

8

7 6

4

2

3

Figure 23. Optional Offset Nulling Circuit

OP77

100kΩ

+18V

–18V

7

6

4

2

3

+

10µF

+

10µF

0.1µF

0.1µF

*

*

10Ω

10Ω

10kΩ

10kΩ

NOTES

*1 PER BOARD

Figure 24. Burn-In Circuit

1MΩ

RL

VX

10Ω

10kΩ

100kΩ

VIN = ±10V

TYPICAL PRECISION

OP AMP

VY

VX

–10V

0V

+10V

NOTES

1. GAIN NOT CONSISTANT. CAUSES NONLINEAR ERRORS.

2. AVO SPEC IS ONLY PART OF THE SOLUTION.

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

AVO

650V/mV

RL = 2kΩ

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.

VY

VX

–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.