RADIO FILTER CIRCUIT AND NOISE REDUCING METHOD

摘要

A filter circuit wherein NF of a Gm-C filter is improved. There are included a filter part that comprises a first capacitance and at least one first transconductance amplifier the mutual conductance of which varies in accordance with a first control signal; a second transconductance amplifier the mutual conductance of which is controlled by the first control signal; a third transconductance amplifier the mutual conductance of which is controlled by a second control signal; and a second capacitance connected to the outputs of the first and second transconductance amplifiers and to the input of the filter part.