Patent ID: 7724101

Claim:
A crystal oscillator circuit comprising: a capacitive load stage coupled to crystal terminals; an amplifier stage that establishes an oscillation signal at an amplifier stage output, wherein the amplifier stage includes: an amplifying transistor coupled to the crystal terminals and to the capacitive load stage; a control transistor coupled directly to the source of the amplifying transistor; a plurality of resistors coupled in series to the control transistor; switching circuitry that selectively switches one or more of the plurality of resistors into a current path through the control transistor in response to a digital configuration signal so as to determine the adjustable range of a bias current through the amplifying transistor; an amplitude control stage configured and coupled to control the amplitude of the oscillation signal by providing a signal to the control transistor; and a pick-up stage coupled to the amplifier stage and to the crystal terminals to generate an oscillator output signal.