Datasheet

10
®
OPA404
FIGURE 7. Voltage-Controlled Microamp Current Source.
FIGURE 9. FET Instrumentation Amplifier with Shield Driver.
FIGURE 8. Sensitive Photodiode Amplifier.
E
1
E
1
Output = 1µA/V
I
O
1
2
3
1MΩ
R
6
5
3
2
INA105
Differential
Input
1
I
O
= (E
1
– E
2
) /R
Load
1/4
OPA404
+15V
Output
0.01µF
Guard
Pin Photodiode
UDT Pin-040A
2
3
8
4
1
–15V
<1pF to prevent gain peaking
5 x 8
8
V/W
0.1µF
0.01µF
1/4 
OPA404
Circuit must be well shielded.
1000MΩ
1000MΩ
12
13
3
1
2
6
7
5
10
9
8
14
1/4
OPA404
1/4
OPA404
1/4
OPA404
1/4
OPA404
Input
+
–
Guard
20kΩ 20kΩ
Guard
R
F

10kΩ
R
F

10kΩ
20kΩ 20kΩ
A
V
= 101µV/V
I ≈ 1pA
R ≈ 10
13
Ω 
BW ≈ 100kHz
Differential Voltage Gain = 1+ (2R
F
/R
G
)
B
IN
R
G
/2
100Ω
R
G
/2
100Ω