Patent ID: 7187245

Claim:
A circuit for controlling the amplitude of oscillation of a crystal, comprising: a peak detector detecting a peak signal from the crystal, the peak detector providing a voltage output; a first voltage-to-current converter coupled with the voltage output of the peak detector, the first voltage-to-current converter providing a peak output current; a first current-to-voltage converter coupled with the first voltage-to-current converter, the first current-to-voltage converter providing a first output voltage; an input for a reference voltage signal; a second voltage-to-current converter coupled with the reference voltage signal, the second voltage-to-current converter providing a reference output current; a second current-to-voltage converter coupled with the second voltage-to-current converter, the second current-to-voltage converter providing a second output voltage; and an amplifier receiving the first and second output voltages, the amplifier having a control output that is proportional to the difference between the first and second output voltages, the control output for controlling the amplitude of oscillation of the crystal.