Current mirror-embedded low-pass filter for subscriber line interface circuit applications

摘要

A current mirror circuit incorporates a resistor-capacitor (RC) filter circuit in the base-coupling path of input and output current mirror transistors, to realize a highly integrated low pass filter current mirror architecture, that reduces implementation complexity, and complies with reduced power supply parameters of a subscriber line interface circuit. A filter resistor is connected in series between the bases of the input and output current mirror transistors. A filter capacitor is coupled between the base of the output transistor and the power supply rail. The effect of this low pass filter circuit is such that the output current is equal to the frequency content of the input current below the cut-off frequency as defined by the RC time constant of the filter.