Datasheet

OP177 Data Sheet
Rev. H | Page 10 of 16
PRECISION HIGH GAIN DIFFERENTIAL AMPLIFIER
The high gain, gain linearity, CMRR, and low TCV
OS
of the
OP177 make it possible to obtain performance not previously
available in single stage, very high gain amplifier applications.
See Figure 28.
For best CMR,
R2
R1
must equal
R4
R3
In this example, with a 10 mV differential signal, the maximum
errors are listed in Table 6.
0.1µF
+15V
R
1
1kΩ
R
3
1kΩ
R
2
1MΩ
0.1µF
–15V
R
4
1MΩ
2
3
7
6
4
00289-027
OP177
–
+
Figure 28. Precision High Gain Differential Amplifier
Table 6. High Gain Differential Amplifier Performance
Type Amount
Common-Mode Voltage 0.1%/V
Gain Linearity, Worst Case 0.02%
TCV
OS
0.0003%/°C
TCI
OS
0.008%/°C
ISOLATING LARGE CAPACITIVE LOADS
The circuit shown in Figure 29 reduces maximum slew rate but
allows driving capacitive loads of any size without instability.
Because the 100 Ω resistor is inside the feedback loop, the effect
on output impedance is reduced to insignificance by the high
open loop gain of the OP177.
–
+
OP177
0.1µF
+15V
R
S
R
F
0.1µF
–15V
2
3
7
6
4
00289-028
INPU
T
100Ω
10pF
C
LOAD
OUTPUT
Figure 29. Isolating Capacitive Loads
BILATERAL CURRENT SOURCE
The current sources shown in Figure 30 supply both positive
and negative currents into a grounded load.
Note that
R1
R3
R2
R4R5
R2
R4
R
Z
O










15
and that for Z
O
to be infinite
R1
R3
must
R2
R4R5


PRECISION ABSOLUTE VALUE AMPLIFIER
The high gain and low TCV
OS
assure accurate operation with
inputs from microvolts to volts. In this circuit, the signal always
appears as a common-mode signal to the operational amplifiers
(for details, see Figure 31).
00289-029
–
+
OP177
R
1
100kΩ
R
3
1kΩ
2
3
6
V
IN
R
2
100kΩ
R
4
990Ω
R
5
10Ω
I
OUT
≤ 15mA
–
+
OP177
R
1
R
3
2
3
6
V
IN
R
2
R
4
R
5
I
OUT
≤ 100mA
50Ω
+15V
–15V
2N2222
2N2907
I
OUT
= V
IN
R
3
R
1
× R
5
GIVEN R
3
= R
4
+ R
5
, R
1
= R
2
BASIC CURRENT SOURCE 100m
A
CURRENT SOURCE
Figure 30. Bilateral Current Source