Transconductance amplifiers, filters with transconductance amplifier and tuning circuit for a transconductance amplifier in the filter

摘要

PROBLEM TO BE SOLVED: To provide a transconductance amplifier circuit which operates with a sufficiently high output impedance at a lower power source voltage and ensures a sufficient output dynamic range.;SOLUTION: This transconductance amplifier circuit is constituted of input and output stages 10 and 11, and the input stage 10 is provided with a differential input circuit 13 for performing voltage/current conversion, a pair of regulated cascode circuits 14 for controlling the output voltage according to a control voltage, and the input side part of a pair of current mirror circuits 15 for returning the output currents. The output stage 11 is provided with the output side part of a pair of current mirror circuits 15, a differential current source circuit, a second pair of regulated cascode circuits 16 for holding the output voltage of the current mirror circuit as a value corresponding to the first bias voltage, and a third pair of regulated cascode circuits 17 for holding the output voltage of the differential current source circuit as a value corresponding to the second bias voltage with a common output.;COPYRIGHT: (C)2002,JPO