Difference Amplifier

This amplifier uses both inverting and non-inverting inputs with a gain of one to produce an output equal to the difference between the inputs. It is a special case of the differential amplifier. You can also choose the resistances to amplify the difference.

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Differential amplifier
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Amplified Difference

This amplifier uses both inverting and non-inverting inputs with a gain of one to produce an output equal to the difference between the inputs. It is a special case of the differential amplifier. You can choose the resistances to get an amplification of one.

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Summing amplifier
Difference amplifier
Differential amplifier
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Rule Application:Difference Amplifier

The behavior of most configurations of op-amps can be determined by applying the "golden rules". For the difference amplifier, the voltage at the non-inverting input is v2/2 , so by the voltage rule that voltage also appears at point A.

Applying the current rule, the current into A must be zero, so

which for equal resistors becomes

Difference amplifierAmplified difference
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Rule Application:Amplified Difference

The voltage at 3 is given by

so by the voltage rule that voltage appears at A. The current rule at A gives
Substitution gives the expression at right.

Difference amplifierAmplified difference
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