LMC662
SNOSC51C –APRIL 1998–REVISED MARCH 2013
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BIAS CURRENT TESTING
The test method of Figure 25 is appropriate for bench-testing bias current with reasonable accuracy. To
understand its operation, first close switch S2 momentarily. When S2 is opened, then
(10)
Figure 25. 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 Ib−, 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)
(11)
where Cx is the stray capacitance at the + input.
Typical Single-Supply Applications
(V+ = 5.0 VDC
)
Additional single-supply applications ideas can be found in the LM358 datasheet. The LMC662 is pin-for-pin
compatible with the LM358 and offers greater bandwidth and input resistance over the LM358. These features
will improve the performance of many existing single-supply applications. Note, however, that the supply voltage
range of the LM662 is smaller than that of the LM358.
Figure 26. Low-Leakage Sample-and-Hold
12
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