OP77
APPLICATIONS
R2
1MΩ
R3
+15V
+15V
0.1µF
R1
1kΩ
R1
R2
2
3
2N2222
2
3
V
7
IN
6
6
OP77
OP77E
2N2907
4
R5
R3
1kΩ
0.1µF
R4
R4
–15V
1MΩ
I
< 100mA
OUT
R3
R1 – R5
GIVEN R3 = R4 + R5, R1 = R2
I
= V
–15V
OUT
IN
(
)
Figure 27. Precision High-Gain Differential Amplifier
Figure 30. 100 mA Current Source
The high gain, gain linearity, CMRR, and low TCVOS of the
OP77 make it possible to obtain performance not previously
available in single-stage, very high-gain amplifier applications.
These current sources can supply both positive and negative
current into a grounded load.
Note that
R1
R2
R3
R4
For best CMR,
must equal
. In this example, with a
R4
R2
⎛
⎜
⎝
⎞
⎟
⎠
R3
R5
+ 1
10 mV differential signal, the maximum errors are as listed in
Table 7.
ZO
=
R5 + R4
R2
R1
Table 7. Maximum Errors
Type
Amount
0.01%/V
0.02%
R5 + R4
R2
R3
R1
And that for ZO to be infinite
must =
Common-Mode Voltage
Gain Linearity, Worst Case
TCVOS
TCIOS
0.003%/°C
0.008%/°C
R
F
10µF
+15V
0.1µF
R
S
2
3
7
INPUT
100Ω
6
OUTPUT
OP77
4
C
LOAD
0.1µF
–15V
Figure 28. Isolating Large Capacitive Loads
This circuit reduces maximum slew rate but allows driving
capacitive loads of any size without instability. Because the boon
resistor is inside the feedback loop, its effect on output
impedance is reduced to insignificance by the high open-loop
gain of the OP77.
R3
1kΩ
R1
100kΩ
2
3
V
IN
6
I
< 15mA
OP77
OUT
R5
10Ω
R2
100kΩ
R4
990Ω
Figure 29. Basic Current Source
Rev. E | Page 11 of 16
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