Circuitry and method for precision amplitude control in quartz and mems oscillators

Abstract

An oscillator includes oscillator circuitry () including a transconductance stage () and a resonator (). A comparator () produces first (CLK) and second (/CLK) clock signals which indicate the timing of positive and negative phases of a differential output signal (V-V) produced by the transconductance circuit in response to the resonator. A synchronous rectifier () converts the differential output signal to a current (I) in response to the first and second clock signals. A switched capacitor notch filter () filters the current in response to the first and second clock signals. A control current (I) which controls the transconductance of the transconductance circuit is generated in response to the notch filter. The resonator may be a MEMS resonator.