A wideband dual-mode LC-VCO with a switchable gate-biased active core

Abstract

A wideband inductance-capacitance voltage-controlled oscillator (VCO) with a gm-switching technique was designed and fabricated in the 65-nm CMOS process. With a switchable secondary gate-biased active core and a primary core, the VCO operates in two different modes. In the LF mode, in which switches turn on the secondary core, the increased start-up gain facilitates LF oscillation. In the HF mode, in which the switches isolate the secondary core from the primary core, the reduced capacitive loading allows for HF oscillation. In addition, since the gate bias of the secondary core transistors guarantees the high transconductance of the secondary core, the switch size can be minimized, which further extends the upper boundary of the oscillation frequency. The VCO achieved a 41\% frequency range, i.e., 3.36-5.1 GHz, and a phase noise of-123.1 dBc/Hz at an offset of 1 MHz from an output frequency of 4.21 GHz. The active silicon area was 0.24 mm2, and the power consumption was 8.7 mW at 5 GHz.