Bias Current Testing

The test method of Figure 8 is appropriate for bench-testing

bias current with reasonable accuracy. To understand its

operation, first close switch S2 momentarily. When S2 is

opened, then

A suitable capacitor for C2 would bea5pFor10pF silver

mica, NPO ceramic, or air-dielectric. When determining the

magnitude of I

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)

where C

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(Input pins are lifted out of PC board and soldered directly to components.

All other pins connected to PC board.)

FIGURE 7. Air Wiring

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FIGURE 8. Simple Input Bias Current Test Circuit

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