A 17 GHz All-npn Push-Pull Class-C VCO

A SiGe BiCMOS push-pull class-C VCO operating at 17 GHz and making use of only npn transistors is presented. A magnetic transformer is used to set positive feedback around a common-collector differential pair and implement the push-pull operation. This allows to halve the bias current for a given amplitude of oscillation, while using just one type of active devices. The oscillator features a phase noise as low as -116 dBc/Hz at 1 MHz offset, while drawing 13.7 mA from the 3.3 V supply. The tuning range is 15%.