COMMON MODE FEEDBACK CIRCUIT, MUTUAL CONDUCTANCE AMPLIFIER, AND gmC FILTER

摘要

PROBLEM TO BE SOLVED: To provide a technology capable of controlling a common mode voltage constant without decreasing an amplification factor of a differential amplifier. SOLUTION: An output voltage of a differential amplifier 12 is given to gates of two MOS transistors Q12, Q13 of a common mode voltage detection circuit 13 and a voltage at a midpoint of resistors R1, R2 connected to the drains is outputted as a common mode detection voltage. A voltage control circuit 15 compares the voltage at the midpoint of the resistors with a reference voltage and carries out feedback to decrease the common mode voltage of the differential amplifier when the voltage at the midpoint of the resistors is lower than the reference voltage, and the voltage control circuit 15 carries out feedback to increase the common mode voltage of the differential amplifier when the voltage at the midpoint of the resistors is higher than the reference voltage. COPYRIGHT: (C)2006,JPO&NCIPI