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

摘要

PURPOSE: A DC offset compensation circuit of a closed loop operational amplifier and a method for compensating DC offset are provided to shorten a settling time of an output signal by compensating rapidly the DC offset of the output signal. CONSTITUTION: A closed loop operational amplifier includes the first closed loop operational amplifier(31) for amplifying an input signal according to the first reference voltage, the second closed loop operational amplifier(33) for amplifying the output input signal of the first closed loop operational amplifier(31) according to the second reference voltage, and a DC offset compensation circuit(35). The DC offset compensation circuit(35) includes a buffer(351), a low pass filter(352), and a comparator(353). The buffer(351) is used for buffering the output signal of the output signal of the second closed loop operational amplifier(33). The low pass filter(352) is used for filtering the output signal of the buffer(351) and detecting a DC voltage value of the filtered output signal. The comparator(353) is used for comparing the DC voltage value to the second reference voltage to generate a compensation voltage and providing the compensation voltage as the first reference voltage to the first closed loop operational amplifier(31).