LMV321M7SLASHNOPB datasheet(22/52 Pages) TI1

22 / 52 page

LMV321-N, LMV321-N-Q1, LMV358-N

LMV358-N-Q1, LMV324-N, LMV324-N-Q1

SNOS012J – AUGUST 2000 – REVISED DECEMBER 2014

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Typical Applications (continued)

9.2.3.1 Three-Op-Amp Instrumentation Amplifier

The quad LMV324 can be used to build a three-op-amp instrumentation amplifier as shown in Figure 57.

Figure 57. Three-Op-Amp Instrumentation Amplifier

The first stage of this instrumentation amplifier is a differential-input, differential-output amplifier, with two voltage

followers. These two voltage followers assure that the input impedance is over 100 M

Ω. The gain of this

instrumentation amplifier is set by the ratio of R2/R1. R3 should equal R1, and R4 equal R2. Matching of R3 to R1

and R4 to R2 affects the CMRR. For good CMRR over temperature, low drift resistors should be used. Making R4

slightly smaller than R2 and adding a trim pot equal to twice the difference between R2 and R4 will allow the

CMRR to be adjusted for optimum performance.

9.2.3.2 Two-Op-Amp Instrumentation Amplifier

A two-op-amp instrumentation amplifier can also be used to make a high-input-impedance DC differential

amplifier (Figure 58). As in the three-op-amp circuit, this instrumentation amplifier requires precise resistor

matching for good CMRR. R4 should equal R1 and, R3 should equal R2.

Figure 58. Two-Op-Amp Instrumentation Amplifier

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Product Folder Links: LMV321-N LMV321-N-Q1 LMV358-N LMV358-N-Q1 LMV324-N LMV324-N-Q1

LMV321M7/NOPB Datasheet(PDF) 22 Page - Texas Instruments