LMC6024 Datasheet, PDF (12/22 Pages) National Semiconductor (TI) – Low Power CMOS Quad Operational Amplifier

LMC6024
SNOS621D – AUGUST 2000 – REVISED MARCH 2013
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BIAS CURRENT TESTING
The test method of Figure 34 is appropriate for bench-testing bias current with reasonable accuracy. To
understand its operation, first close switch S2 momentarily. When S2 is opened, then
(1)
Figure 34. Simple Input Bias Current Test Circuit
A suitable capacitor for C2 would be a 5 pF or 10 pF silver mica, NPO ceramic, or air-dielectric. When
determining the magnitude of I^−, the leakage of the capacitor and socket must be taken into account. Switch S2
should be left shorted most of the time, or else the dielectric absorption of the capacitor C2 could cause errors.
Similarly, if S1 is shorted momentarily (while leaving S2 shorted)
(2)
where C_x is the stray capacitance at the +input.
Typical Single-Supply Applications
(V⁺ = 5.0 V_DC)
A 5V bias on the photodiode can cut its capacitance by a factor of 2 or 3, leading to improved response and lower
noise. However, this bias on the photodiode will cause photodiode leakage (also known as its dark current).
Figure 35. Photodiode Current-to-Voltage Converter
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