2
3
1
1/4
OPA404
1
Output = 1µA/V
Differential
Input
3
2
E1
1MΩ
IO
6
5
E1
R
Load
I
O = (E1 – E2) /R
INA105
FIGURE 7. Voltage-Controlled Microamp Current Source.
<1pF to prevent gain peaking
1000MΩ
Pin Photodiode
UDT Pin-040A
Guard
0.01µF
+15V
2
3
8
Output
1/4
OPA404
1
4
0.1µF
5 x 88 V/W
0.01µF
1000MΩ
–15V
Circuit must be well shielded.
FIGURE 8. Sensitive Photodiode Amplifier.
3
20kΩ
20kΩ
1/4
OPA404
2
1
RF
10kΩ
Guard
RG/2
+
100Ω
12
13
10
1/4
OPA404
1/4
8
Input
–
OPA404
14
9
RG/2
100Ω
Guard
AV = 101µV/V
IB ≈ 1pA
RIN ≈ 1013Ω
BW ≈ 100kHz
Differential Voltage Gain = 1+ (2RF/RG)
RF
10kΩ
6
5
1/4
OPA404
7
20kΩ
20kΩ
FIGURE 9. FET Instrumentation Amplifier with Shield Driver.
®
10
OPA404
BB [ BURR-BROWN CORPORATION ]
