Trans-conductance amplification circuit, trans-conductance filter circuit, and filtering method

摘要

A trans-conductance filter circuit with an expanded cut-off frequency range is provided. The cut-off frequency of a trans-conductance filter circuit is changed by varying the current mirror ratio of a current mirror circuit. This mirror ratio is varied by changing the output current of a constant current source, or by switching among the respective action states of multiple transistors the actions of which are invoked within constant current regions. The variable cut-off frequency range can be expanded without losing the constant current attributes of the transistors.