Current-controlled quadrature oscillator using differential gm/C cells incorporating amplitude limiters

摘要

An oscillator includes a series of N number of gm/C stages where each gm/C stage has a pair of input terminals and a pair of output terminals. The pair of output terminals of each gm/C stage is coupled to the pair of input terminals of the next gm/C stage except the pair of output terminals of the last gm/C stage is cross-coupled to the pair of input terminals of the first gm/C stage whereby the oscillator oscillates in quadrature. Each gm/C stage includes a differential pair of transistors, a tunable current source, a capacitor, an amplitude limiter circuit and an active load and common mode bias circuit. The capacitor and the amplitude limiter circuit are coupled between the pair of output terminals of the gm/C stage. The amplitude limiter circuit operates to limit the voltage magnitude of the output signal at the pair of output terminals of the gm/C stage.