A 2.5 GHz low phase noise silicon germanium heterojunction bipolar transistor ring oscillator

This paper presents the modelling of phase noise for a two-stage single-ended silicon germanium (SiGe) heterojunction bipolar transistor-based ring oscillator using the impulse sensitivity function. It is shown that the lower flicker noise characteristic of the SiGe technology at low frequencies translates into low-frequency phase noise improvements. The ring oscillator has a computed phase noise of −80 dBc/Hz at 1 MHz offset for a 2.5 GHz signal. The figure of merit obtained for this oscillator is −142 dBc/Hz.