The input offset voltage of operational amplifiers (op-amps) arises from unavoidable mismatches in the differential input stage of the op-amp circuit caused by mismatched transistor pairs, collector currents, current-gain betas(B), collector or emitter resistors, etc. This application report describes the effects of mismatched components on the input offset voltage, and proposes using an external null circuit to reduce the input offset voltage of an amplifier. It also suggests a means for computing proper values of resistors in the null circuit in order to provide appropriate input-offset-voltage compensation.

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