Voltage controlled CMOS oscillator

摘要

The frequency of oscillation of two cross-coupled CMOS inverters with a parallel LC tank connected between the two drains can be varied by a control voltage which varies the capacitance value of the tank circuit. The gate-to-source capacitance is used as the variable capacitance. The gate-to-source capacitance is varied by changing the dc gate voltage, which can be effected by either changing the dc current through the inverters or by varying the dc voltage across the inverters. The control voltage may also be made to vary with temperature such that the free running frequency of the oscillator is held constant with varying temperature.