Patent ID: 8581644

Claim:
A system incorporating a phase locked loop circuit, the system comprising: a voltage controlled oscillator (VCO) having a first input terminal for selecting phase and frequency characteristics of an output signal and an output terminal on which the output signal is provided; a phase and frequency detector which generates first VCO input signals indicative of a phase difference between the VCO output signal and a reference signal and whether there is a frequency difference between the VCO output signal and the reference signal; circuitry coupled to convert the first VCO input signals into digital signals and to generate an integral path input signal therefrom; and first integral path circuitry comprising a first transistor device and a programmable low pass filter, the programmable low pass filter coupled to receive the integral path input signal and provide a low pass filtered version of the integral path input signal to a first terminal of the first transistor device to control conduction through the first transistor device and provide a first adjustment signal from the first transistor device for adjustment of the frequency of the VCO output signal, wherein the first transistor device is a field effect transistor and the low pass filtered version of the integral path input signal is provided as an input to a gate terminal of the first transistor device to control conduction between a supply voltage terminal and the first input signal of the VCO having a first input terminal.