Patent ID: 8970311
Filing Date: 2015-03-03
Classification: H03L

Abstract:
1. A voltage-controlled oscillator (VCO) having an output signal having a frequency responsive to a tuning signal, comprising: a plurality of inverters coupled to form a loop, each inverter having a differential pair of transistors configured to steer a tail current from a current source transistor, the current source transistor sourcing the tail current responsive to a bias voltage, each inverter stage including a plurality of switched-capacitor circuits configured to control a signal delay through the inverter stage in response to the tuning signal so as to control the frequency of the output signal; a node to provide a power supply signal; and a bias circuit configured to generate the bias voltage responsive to the power supply signal, coupled from the node to the bias circuit via an additional switched-capacitor circuit, and a reference signal such that an amplitude of the output signal is substantially independent of the output signal frequency and depends upon the reference signal; wherein the amplitude of the output signal remains fixed at the difference between the power supply signal and the reference signal and is independent of the tuning signal.