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AN4586

2-op amp instrumentation amplifier

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2-op amp instrumentation amplifier

The 2-op amp instrumentation amplifier configuration is composed of one additional op-amp

compared to the differential configuration. Because of this, the signal “sees” a high

impedance and consequently is not impacted.

Figure 4 shows the 2-op amp instrumentation amplifier schematic.

Figure 4. 2-op amp instrumentation amplifier schematic

If we do not consider the inaccuracies, we have Equation 6 at the output.

Equation 6

amp, we get Equation 7:

Equation 7

So, we get Equation 8:

Vout2

V2 1

Rf2

Rg2

-----------

+

⎝⎠

⎛⎞ V1 Rf2

Rg2

-----------

1

Rf1

Rg1

-----------

+

⎝⎠

⎛⎞

–

=

Vout2

V2 V1

–

() 1

R

α

R

β

-------

+

⎝⎠

⎛⎞

Vio2 Vio1

–

() 1

R

α

R

β

-------

+

⎝⎠

⎛⎞

–

=