AN4586 datasheet(10/19 Pages) STMICROELECTRONICS

Part #	AN4586

Description	Signal conditioning, differential to single-ended amplification

PDF	19 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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10 / 19 page

3-op amp instrumentation amplifier

AN4586

10/19

DocID026915 Rev 1

3-op amp instrumentation amplifier

The 3-op amp instrumentation amplifier configuration has been designed to improve the

CMRR impacted by the resistors, and thus to improve measurement accuracy when Vicm

varies.

Figure 6 shows the schematic of a 3-op amp instrumentation amplifier.

Figure 6. 3-op amp instrumentation amplifier schematic

The output voltage of the 3-op amp instrumentation amplifier is defined by Equation 10.

Equation 10

By considering R1 = Rx(1+εR1), R3 = Rx(1+εR3), R2 = Ry(1+εR2), R4 = Ry(1+εR4),

R5 = Rf(1+εR5), and R6 = Ry(1+εR6), the Gdiff, Gcm and Voffset parameters become as

shown in Equation 11, Equation 12, and Equation 13 respectively.

Equation 11

Equation 12

Vout3

Gdiff

Vdiff Gcm

Vicm Voffset

⋅

Gcm

Rx Ry

---------------------

εR1 εR4 εR2

–

εR3

–

()

AN4586 Datasheet(PDF) 10 Page - STMicroelectronics