OP77
TEST CIRCUITS
200kΩ
TYPICAL PRECISION
OP AMP
50Ω
10kΩ
100kΩ
V
Y
V
O
OP77
1MΩ
10Ω
V
= ±10V
IN
V
V
X
O
V
=
V
OS
X
4000
–10V
0V
+10V
R
L
Figure 21. Typical Offset Voltage Test Circuit
A
650V/mV
VO
R
= 2kΩ
L
2.5MΩ
NOTES
1. GAIN NOT CONSISTANT. CAUSES NONLINEAR ERRORS.
2. A SPEC IS ONLY PART OF THE SOLUTION.
V+
VO
100Ω
100Ω
2
3
7
3. CHECK SPECIFICATION TABLE 1 AND TABLE 2 FOR PERFORMANCE.
3.3kΩ
6
OUTPUT
(≈10Hz FILTER)
Figure 25. Open-Loop Gain Linearity
OP77
4.7µF
4
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.
V–
V
O
INPUT REFERRED NOISE =
25,000
Figure 22. Typical Low-Frequency Noise Test Circuit
20kΩ
V+
1
2
8
V
Y
–
7
6
OUTPUT
INPUT
+
OP77
3
4
V–
Figure 23. Optional Offset Nulling Circuit
V
–10V
0V
+10V
X
100kΩ
+18V
+
*
10µF
2
10Ω
0.1µF
Figure 26. Output Gain Linearity Trace
7
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.
6
OP77
3
4
10kΩ
10kΩ
0.1µF
10Ω
*
10µF
+
–18V
NOTES
*
1 PER BOARD
Figure 24. Burn-In Circuit
Rev. E | Page 10 of 16
ADI [ ADI ]
