An apparatus and method for providing a stable gain over wide frequency
range in a VCO are presented. A VCO uses a waveform generator along with
a bias generator having a frequency select input. The frequency select
input is used to adjust the amount of output current and/or gain of the
bias generator. The output current of the bias generator determines the
frequency of the output of the waveform generator. Multiple bias and
waveform generators may be used to expand the frequency range of the VCO.
A PLL may be programmed for a variety of output frequencies by using the
frequency select input of the VCO.