MOSFET-C filter with on-chip tuning and wide programming range

Abstract

This paper describes a complete system that includes a signal processing circuit, i.e., a bandpass audio filter, with its surrounding Q and f/sub c/ tuning circuitry. The filter is not only tunable against fabrication tolerances or aging, but also programmable by the user in a wide range for both parameters. To achieve this goal, a novel phase-locked loop architecture has been designed and implemented. For the amplitude detection and control of both voltage-controlled oscillator and Q-tuning circuit, a novel scheme is also proposed. The complete system has been implemented on a 0.5-/spl mu/m CMOS technology.