OPA404_15 Datasheet, PDF (9/16 Pages) Texas Instruments – Quad High-Speed Precision OPERATIONAL AMPLIFIER

BIAS CURRENT CHANGE
vs COMMON-MODE VOLTAGE
The input bias currents of most popular BIFET operational
amplifiers are affected by common-mode voltage (Figure 4).
Higher input FET gate-to-drain voltage causes leakage and
ionization (bias) currents to increase. Due to its cascode
input stage, the extremely low bias current of the OPA404 is
not compromised by common-mode voltage.
80
70 ^{TA = +25°C; curves taken from}
mfg. published typical data
60
LF156/157
50
40
30 ^LF156/157
AD547
LF155
20
10 ^LF155
AD547
0 _OPA404
–10 OP-15/16/17
–20
–15
–10
–5
0
+5
Common-Mode Voltage (VDC)
OPA404
+10
+15
FIGURE 4. Input Bias Current vs Common-Mode Voltage.
APPLICATIONS CIRCUITS
Figures 5 through 11 are circuit diagrams of various appli-
cations for the OPA404.
Operate
In
Zero
10kΩ
100Ω
1MΩ
2
1/4
1
3 ^OPA404
100kΩ
100kΩ
Polypropylene
1µF
6
7
1/4
OPA404
5
Out
Gain = –100
V_OS < 10µV
Drift ≈ 0.05µV/°C
Zero Droop ≈ 1µV/s
Referred to Input
FIGURE 5. Auto-Zero Amplifier.
Input
≈10pF
10kΩ
(1)
1MΩ
IN914
2
1/4
1
(1)
(1)
3 ^OPA404
IN914
2N4117
6
1/4
7
5 ^OPA404
Output
Droop ≈ 0.1mV/s
0.01µF Polstyrene
NOTE: (1) Reverse polarity for negative peak detection.
FIGURE 6. Low-Droop Positive Peak Detector.
®
9
OPA404