Patent ID: 7145391

Claim:
A method for compensating for bias currents associated with first and second inputs of a differential amplifier, comprising: using a feedback loop, including an operational amplifier (A 1 ) and a transistor (Q 4 ), to produce a compensation current that is substantially equal in magnitude but opposite in polarity to the input bias currents associated with the first and second inputs of the differential amplifier; and replicating the compensation current to thereby produce first and second replicated compensation currents that are substantially the same as the compensation current; providing the first replicated compensation current to the first input of the differential amplifier to thereby substantially cancel the input bias current at the first input; and providing the second replicated compensation current to the second input of the differential amplifier to thereby substantially cancel the input bias current at the second input; wherein the transistor (Q 4 ) includes a control terminal and a current path including a first current path terminal and a second current path terminal; wherein an output of the operation amplifier (A 1 ) is provided to either the control terminal or the first current path terminal of the transistor (Q 4 ); and wherein the compensation current is a current at the second current path terminal of the transistor (Q 4 ).