10.0 Instrumentation Circuits

The LMC6484 has the high input impedance, large

common-mode range and high CMRR needed for designing

instrumentation circuits. Instrumentation circuits designed

with

the

LMC6484

can

reject

a

larger

range

of

common-mode signals than most in-amps. This makes in-

strumentation circuits designed with the LMC6484 an excel-

lent choice for noisy or industrial environments. Other appli-

cations that benefit from these features include analytic

medical instruments, magnetic field detectors, gas detectors,

and silicon-based transducers.

A small valued potentiometer is used in series with Rg to set

the differential gain of the 3 op-amp instrumentation circuit in

Figure 15. This combination is used instead of one large val-

ued potentiometer to increase gain trim accuracy and reduce

error due to vibration.

A 2 op-amp instrumentation amplifier designed for a gain of

100 is shown in

Figure 16. Low sensitivity trimming is made

DS011714-28

FIGURE 14. Operating from the same

Supply Voltage, the LMC6484 buffers the

ADC12038 maintaining excellent accuracy

DS011714-29

FIGURE 15. Low Power 3 Op-Amp Instrumentation Amplifier

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