Datasheet

LMC6022

SNOS622D –NOVEMBER 1994–REVISED MARCH 2013

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Figure 32. 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

is the stray capacitance at the + input.

Typical Single-Supply Applications

(V+ = 5.0 V

)

Note: 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 33. Photodiode Current-to-Voltage Converter

(Upper limit of output range dictated by input common-mode range;

lower limit dictated by minimum current requirement of LM385.)

Figure 34. Micropower Current Source Figure 35. Low-Leakage Sample-and-Hold

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