LMC6484 Datasheet, PDF (35/45 Pages) National Semiconductor (TI) – CMOS Quad Rail-to-Rail Input and Output Operational Amplifier

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LMC6484
SNOS675C – AUGUST 2000 – REVISED SEPTEMBER 2015
System Examples (continued)
8.3.2 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 instrumentation circuits designed with the LMC6484 an
excellent choice for noisy or industrial environments. Other applications 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-opamp instrumentation
circuit in Figure 74. This combination is used instead of one large valued potentiometer to increase gain trim
accuracy and reduce error due to vibration.
Figure 74. Low-Power 3-Opamp Instrumentation Amplifier
A 2-opamp instrumentation amplifier designed for a gain of 100 is shown in Figure 75. Low sensitivity trimming is
made for offset voltage, CMRR and gain. Low cost and low power consumption are the main advantages of this
2-opamp circuit.
Higher frequency and larger common-mode range applications are best facilitated by a 3-opamp instrumentation
amplifier.
Figure 75. Low-Power 2-Opamp Instrumentation Amplifier
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