DC OFFSET COMPENSATION CIRCUIT OF CLOSED LOOP OPERATIONAL AMPLIFIER, METHOD OF COMPENSATING FOR DC OFFSET AND CLOSED LOOP OPERATIONAL AMPLIFIER

摘要

PROBLEM TO BE SOLVED: To provide a DC offset compensation circuit and a method thereof capable of reducing the settling time of an output signal by fast compensating a DC offset of output signal although a DC voltage of an input signal varies in a closed loop operational amplifier. SOLUTION: This closed loop operational amplifier includes a first closed loop operational amplifier 31 for amplifying an input signal with a compensation voltage as the reference and a second closed loop operational amplifier 33 for amplifying the output signal of the first closed loop operational amplifier with a reference voltage as the reference to generate a final output signal. The DC offset compensation circuit 35 receives the final output signal, detects a DC voltage of the final output signal that varies with the variation in a DC voltage of the input signal, and supplies the compensation voltage corresponding to the detected DC voltage to the first closed loop operational amplifier. The DC offset compensation circuit 35 includes a buffer 351, a low-pass filter 352 for DC voltage value detection and a comparator 353a for compensation voltage generation. COPYRIGHT: (C)2004,JPO