OP77
R1
PRECISION CURRENT SINKS
V+
200Ω
IRF520
OP77
V
R
IN
L
I
=
O
V
IN
R1
> 0V
V
IN
I
O
I
=
V
O
IN
R1
> 0V
V
IN
I
200Ω
O
V
IN
IRF520
OP77
FULL SCALE OF 1V.
= 1A/V
R
L
I
O
R1
1Ω
1W
V–
Figure 32. Positive Current Source
The simple high-current sinks, shown Figure 31 and Figure 32,
require the load to float between the power supply and the sink.
Figure 31. Positive Current Sink
In these circuits, the high gain, high CMRR, and low TCVOS of
the OP77 ensure high accuracy.
The high gain and low TCVOS ensure accurate operation with
inputs from microvolts to volts. In Figure 33, the signal always
appears as a common-mode signal to the op amps. The
OP77EZ CMRR of 1 μV/V ensures errors of less than 2 ppm.
1kΩ
1kΩ
+15V
+15V
0.1µF
C1
D1
0.1µF
30pF
1N4148
2
3
7
6
2
3
7
V
D2
OUT
0 < V
OP77E
< 10V
6
OUT
OP77E
4
2N4393
V
IN
0.1µF
4
R3
2kΩ
0.1µF
–15V
–15V
Figure 33. Precision Absolute Value Amplifier
15V
2
2
2
+
10µF
REF-01
REF-01
REF-01
V
OP77
OUT
100Ω
6
6
6
V
V
V
O
O
O
4
4
4
100Ω
100Ω
0.1µF
Figure 34. Low Noise Precision Reference
Rev. E | Page 12 of 16
ADI [ ADI ]
