Filter circuit

摘要

Input conversion noises of a filter circuit are reduced. The circuit has plural element circuits obtained by dividing the filter circuit so as to include at least one voltage controlled current source, at least one element circuit is an amplification element circuit having an amplifying function for amplifying an input signal to the filter circuit at a set amplification factor. The amplification element circuit has: a loop circuit constructed by plural intra-loop voltage controlled current sources in which mutual conductance values have a predetermined corresponding relation; and a corresponding capacitor connected to a contact in the loop circuit and having a capacitance depending on the corresponding relation so as to set a potential at the contact to a predetermined potential corresponding to the amplification factor, and amplification element circuit has an electric nature which is independent on the amplification factor when seeing from the input side of the filter circuit.