Voltage-controlled oscillators with controlled operating range and related bias circuits and methods

摘要

A voltage-controlled oscillator includes a bias circuit and a delay circuit. The bias circuit may generate a bias voltage signal pair having levels that are based on the voltage level of an input voltage signal and that are constrained by the values of a maximum current signal and a minimum current signal that are generated in the bias circuit. The delay circuit generates an output signal having a frequency that varies in response to the bias voltage signal pair. Because an operating frequency range of a voltage-controlled oscillator VCO is limited by a bias circuit, the VCO can operate with reduced gain and can limit the maximum operating frequency to a predetermined level. The VCO may also include a PTAT current generator in the bias circuit which can allow the VCO to compensate for variations of the VCO output frequency based on temperature.