Datasheet

®
8
OPA128
FIGURE 3. High Impedance (10
15
Ω) Amplifier.
OPA128
6
3
2
500Ω 9.5kΩ
8
7
4
5
1
+15V
–15V
Guard
pH Probe
R
50mV Output
≈ 500MΩ
S
1VDC
Output
Offset Trim
100kΩ
FIGURE 5. FET Input Instrumentation Amplifier for Biomedical Applications.
Output
OPA128
2
3
Ω10k
F
R
6
OPA128
3
2
6
Ω10k
F
R
6
1
5
3
2
Ω25k Ω25k
Ω25k
Burr-Brown
INA105
Differential
Amplifier
Ω25k
Differential Voltage Gain = 1 + 2R
F
/R
G
+In
–In
Ω202
G
R
I
B
≈ 100fA
Gain = 100
CMRR ≈ 118dB
R
IN
≈ 10
15
Ω
FIGURE 6. Low-Droop Positive Peak Detector.
OPA128
2
3
6
Output
8
1000µF
Polystyrene
1N914
2N4117A
NOTE: (1) Reverse polarity
for negative peak detection.
1MΩ
10kΩ
1N914
10pF≈
2
3
6
Input
100µV/s≈Droop
OPA606
(1)
(1)
(1)
FIGURE 4. Piezoelectric Transducer Charge Amplifier.
OPA128
2
3
Output
10pF
8
100pF
11
Ω10
F
R
F
C
O
e
11
Ω10
Q∆
Low Frequency Cutoff =
1/(2
F
C
F
) = 0.16Hz
O
e= –∆Q/C
F
6
Rπ