Patent ID: 7456694

Claim:
A tunable oscillator comprising: a voltage-to-current converter having an input for receiving a voltage from a phase-locked loop and an output for outputting a first current converted from the voltage; a current-controlled oscillator having an input for receiving the first current and an output for outputting an output frequency responsive to the voltage; a second current input into the current-controlled oscillator for adjusting the gain of the current-controlled oscillator; a third current input into the voltage-to-current converter for adjusting the first current and the gain of the voltage-to-current converter; and a control circuit for adjusting the second and third currents so that the output frequency spans a lock-in frequency range required by the phase-locked loop, wherein the control circuit uses a linear approximation to pre-set the second current to a value approaching a current value that will produce an output frequency equal to the lower frequency of the lock-in frequency range.