Patent ID: 7411466

Claim:
An overtone crystal oscillator, comprising: a crystal having first and second terminals and having a fundamental resonance frequency and at least one overtone resonance frequency; a plurality of amplifiers coupled in series between said first and second terminals, comprising: a first inverting amplifier having an input coupled to said first terminal of said crystal and having an output; a second inverting amplifier having an input coupled to said output of said first inverting amplifier and having an output; and a third inverting amplifier having an input coupled to said output of said second inverting amplifier and having an output coupled to said second terminal of said crystal; and a resistor-capacitor (RC) network coupled to said plurality of amplifiers, comprising: a first capacitor coupled between said output of said first inverting amplifier and said input of said third inverting amplifier; a second capacitor coupled between said input of said third inverting amplifier and said input of said first inverting amplifier; a third capacitor coupled between said output of said third inverting amplifier and said input of said first inverting amplifier; a first pair of resistors coupled in series between said input and said output of said first inverting amplifier and forming a first intermediate node; and a second pair of resistors coupled in series between said input and said output of said third inverting amplifier and forming a second intermediate node which is coupled to said first intermediate node; wherein said plurality of amplifiers and said RC network are collectively configured to suppress oscillation of said crystal at said fundamental resonance frequency and to enable oscillation at said at least one overtone resonance frequency of said crystal.