A Controllable KVCO Ring VCO Topology

A differential ring Voltage Controlled Oscillator (VCO) with a controllable KVCO is introduced. The capability to control KVCO enables post-fabrication calibration of VCO gain, in order to reduce its vulnerability to Process, Voltage, and Temperature (PVT) variations. Performance of the proposed circuit topology, and its application in design of Phase-Locked Loops (PLLs), are analyzed. The gain of the proposed VCO can be tuned over ±20% of its nominal value. Simulations show that phase noise of the proposed circuit varies by less than 2 dBc/Hz compared to the conventional topology, at an offset frequency of 10 MHz, over its entire KVCO tuning range.