Offset current trim circuit

摘要

Apparatus and methods are disclosed related to trimming an input offset current of an amplifier. One such apparatus can include auxiliary bipolar transistors connected in parallel with bases of respective bipolar transistors of an input stage of an amplifier. The auxiliary bipolar transistors can be biased such that the base currents of the auxiliary bipolar transistors compensate for a mismatch in base currents of the bipolar transistors of the input stage of an amplifier. The offset current at an input of an amplifier can be reduced independent of an offset voltage at the input of the amplifier.

主权项

1. An apparatus comprising:
a first bipolar transistor; a second bipolar transistor; a first auxiliary bipolar transistor having a base electrically connected in parallel with a base of the first bipolar transistor; a first auxiliary current source configured to bias the first auxiliary bipolar transistor; a second auxiliary bipolar transistor having a base electrically connected in parallel with a base of the second bipolar transistor; a second auxiliary current source configured to bias the second auxiliary bipolar transistor, wherein the first auxiliary current source and the second auxiliary current source are configured to bias the first auxiliary bipolar transistor and the second auxiliary bipolar transistor to compensate for a mismatch between current at the base of the first bipolar transistor and current at the base of the second bipolar transistor; and an other current source configured to bias at least one of the first bipolar transistor or the second bipolar transistor.