BIAS CURRENT TESTING

The test method of

Figure 8 is appropriate for bench-testing

bias current with reasonable accuracy. To understand its op-

eration, first close switch S2 momentarily. When S2 is

opened, then

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

must be taken into account. Switch S2 should be left shorted

most of the time, or else the dielectric absorption of the ca-

pacitor C2 could cause errors.

Similarly, if S1 is shorted momentarily (while leaving S2

shorted)

where C

Additional single-supply applications ideas can be found in

the LM358 datasheet. The LMC6032 is pin-for-pin compat-

ible 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

LMC6032 is smaller than that of the LM358.

if R1 = R5;

R3 = R6,

and R4 = R7.

= 100 for circuit shown.

For good CMRR over temperature, low drift resistors should

be used. Matching of R3 to R6 and R4 to R7 affects CMRR.

Gain may be adjusted through R2. CMRR may be adjusted

through R7.

DS011135-11

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

All other pins connected to PC board.)

FIGURE 7. Air Wiring

DS011135-12

FIGURE 8. Simple Input Bias Current Test Circuit

Instrumentation Amplifier

DS011135-14

Sine-Wave Oscillator

DS011135-15

Oscillator frequency is determined by R1, R2, C1, and C2:

where R = R1 = R2 and C = C1 = C2.

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