2.4-GHz band low-voltage class-C PMOS VCO IC with amplitude feedback loop

A novel 2.4 GHz-band 0.5-V Class-C PMOS VCO IC with an amplitude feedback loop is proposed. The amplitude feedback loop circuit consists of a detector, an invertor and a bias control circuit. The feedback loop automatically changes the bias of LC-VCO and shifts the oscillation mode from initial Class-AB to Class-C in steady-state. The Class-C VCO IC is designed, fabricated and fully evaluated in 180-nm CMOS technology. The fabricated VCO IC has exhibited a measured phase noise of -117.4 dBc/Hz at 1 MHz offset from the 2.25 GHz carrier frequency with a supply voltage of only 0.5-V.