+

-

+

-

-

+

a

V

-

V

+

V

-

V

+

V

-

V

+

V

-

V

+

+

-

+

-

+

-

+

-

LMP2234

www.ti.com

SNOSAW4D – SEPTEMBER 2007 – REVISED MARCH 2013

Figure 48. Noise Reduction Circuit

PRECISION INSTRUMENTATION AMPLIFIER

Measurement of very small signals with an amplifier requires close attention to the input impedance of the

amplifier, the gain of the signal on the inputs, and the gain on each input of the amplifier. This is because the

difference of the input signal on the two inputs is of interest and the common signal is considered noise. A

classic circuit implementation that is used is an instrumentation amplifier. Instrumentation amplifiers have a finite,

accurate, and stable gain. They also have extremely high input impedances and very low output impedances.

Finally they have an extremely high CMRR so that the amplifier can only respond to the differential signal. A

typical instrumentation amplifier is shown in Figure 49.

Figure 49. Instrumentation Amplifier

Copyright © 2007–2013, Texas Instruments Incorporated

Submit Documentation Feedback

19

Product Folder Links: LMP2234