Operational amplifier offset trim that does not change the offset potential temperature drift

摘要

A JFET operational amplifier input stage is disclosed along with am offset potential trimming circuit. The trimming circuit includes a scaled down compensation stage that is modeled after the input stage and provided with a constant temperature independent bias. This generates a trimming current that varies with temperature inversely with the transconductance of the input stage. A control circuit applies a digitally controlled portion of the trimming current to the input stage so as to compensate the offset potential. The input offset potential is therefore compensated without changing the offset potential temperature drift. Desirably the compensation is achieved after device assembly.