Ultra-low-power 2.4 GHz Colpitts oscillator based on double feedback technique

This paper presents an oscillator design technique for low-power applications. The circuit is based on the common-gate Colpitts oscillator with additional positive feedback provided by an inductive gate degeneration. This technique decreases the required transconductance to start-up oscillations, which makes possible to reduce the power consumption. Two prototypes were designed in a standard 0.18 μm CMOS technology. The first one presents an oscillating frequency of 2.52 GHz with a phase noise of -122.5 dBc/Hz at a 3 MHz offset frequency and consumes 120.8 μW. The other oscillator has a power consumption of 1 mW and oscillates at 2.38 GHz with a phase noise of -132.7 dBc/Hz at a 3 MHz offset.