OPA128 Datasheet, PDF (8/11 Pages) Burr-Brown (TI) – Difet Electrometer-Grade OPERATIONAL AMPLIFIER

500Ω
9.5kΩ
Guard
+15V
2
8
3
OPA128
76
4
1VDC
Output
5
1
Offset Trim
pH Probe
R_S ≈ 500MΩ
50mV Output
100kΩ
–15V
FIGURE 3. High Impedance (10¹⁵Ω) Amplifier.
∆Q
100pF
C_{F 10pF}
R_F
10¹¹â„¦
28
6
3 ^OPA128
Output
e_O
10¹¹â„¦
e_O = – ∆Q/C_F
Low Frequency Cutoff =
1/(2 π R_F C_F) = 0.16Hz
FIGURE 4. Piezoelectric Transducer Charge Amplifier.
I_B ≈ 100fA
3
Gain = 100
–In
6
CMRR ≈ 118dB
OPA128
2
R_IN ≈ 10¹⁵Ω
R_F
10kΩ
25k Ω
2
25k Ω
5
R_G
202Ω
+In
R_F
10kΩ
3 ^25kΩ
2
6
OPA128
3
25k Ω
1
Differential Voltage Gain = 1 + 2R_F /R_G
6
Burr-Brown
INA105
Differential
Amplifier
Output
FIGURE 5. FET Input Instrumentation Amplifier for Biomedical Applications.
Input
≈10pF
10k Ω
(1)
1N914
2
6
3 ^OPA606
1M Ω
(1)
1N914
(1)
2N4117A
NOTE: (1) Reverse polarity
for negative peak detection.
FIGURE 6. Low-Droop Positive Peak Detector.
2
8
6
OPA128
3
Output
1000µF
Polystyrene
Droop ≈ 100µV/s
®
OPA128
8