Abstract: A ring oscillator includes a set of metal-oxide-semiconductor (MOS) complementary, inverting stages, wherein each stage includes a pair of cross-coupled CMOS NAND or NOR gates. The first and last stages are also cross-coupled, such that positive and negative output signals of the last stage are connected respectively to negative and positive input signals of the first stage.

Abstract: A signal source for generating a well-controlled, predictable oscillating output signal within a short, predetermined and constant start-up time is disclosed. The invention includes a switchable current source for selectively providing an electrical signal to a tank circuit which, in response, provides an oscillating output signal. A control circuit, comprising a comparator is connected to the tank circuit for providing a control signal to the switchable current source which causes the current source to switch in response to the output signal. Particular embodiments of the invention include means for controlling the amplitude of the oscillating output signal, means for controlling the transconductance of the current source, and means for starting the signal source.

Abstract: A loop filter for a phase locked loop system having a voltage controlled oscillator (VCO), a divide-by-N circuit responsive to the output of the VCO, and an edge sensitive phase/frequency comparator responsive to the output of the divide-by-N circuit and a reference timing signal for providing a first control signal when the output of the divide-by-N circuit lags the reference timing signal or a second control signal when the output of the divide-by-N circuit leads the reference signal. The loop filter specifically includes first and second capacitors serially coupled between an output node and a ground reference node, wherein the second capacitor is connected to the ground reference node and the output node provides a control voltage to the VCO. A first current source is controllably connected by a first switch to the output node in response to the first control signal, whereby the first current source charges the first and second serially coupled capacitors.