GAIN VARIABLE AMPLIFIER CIRCUIT

摘要

PROBLEM TO BE SOLVED: To provide a gain variable amplifier circuit enabling the correction of an offset at a high speed. SOLUTION: The plus component signal and minus component signal of the output signal from a gain variable differential amplifying section 11-3 at a third stage and a reference signal extracted from the output signal from the gain variable differential amplifying section 11-1 at a first stage are compared respectively. Two Common Mode potentials corresponding to each signal of the plus component signal and the minus component signal are extracted. The potential difference of the two extracted Common Mode potentials is detected by operational amplifiers 17 and 18. A feedback signal based on the Common Mode potential of the output signal from the gain variable differential amplifying section 11-3 at the third stage is fed back to the gain variable differential amplifying section 11-1 at the first stage so that the potential difference is eliminated. COPYRIGHT: (C)2005,JPO&NCIPI