A balanced 1.5 GHz voltage controlled oscillator with an integrated LC resonator

A monolithic voltage-controlled oscillator (VCO) is presented for low-power digital radio handsets. This circuit is fabricated in a production 0.8/spl mu/m 11GHz f/sub T/ BiCMOS process. The VCO is based on the common-collector Colpitts circuit in a balanced configuration to provide differential output for direct compatibility with prescaler and double-balanced mixer inputs. The circuit utilizes an integrated LC resonator comprised of coplanar inductors, polysilicon capacitors, and on-chip varactors. The fully-integrated inductors have an unloaded Q of approximately 5 at 2GHz.