20-GHz Differential Colpitts VCO in 0.35-μm BiCMOS

This work presents a differential Colpitts voltage controlled oscillator (VCO) with 8% tuning range at 20 GHz based upon the understanding on symbolic expressions of negative resistance and phase noise theory. Implemented in a 0.35-μm BiCMOS technology with fT = 60 GHz, the VCO has an output power of −4.8 dBm. The lowest phase noise is −85 dBc/Hz, and −111 dBc/Hz at 100-kHz and 1-MHz offset, respectively. The power consumption of oscillator core is 34 mW under a −3-V supply. The chip only occupies an area of 370 μm × 610 μm. Moreover, a comparison between two topologies of Colpitts VCO shows that the proposed topology is prior to the conventional in high frequency applications.