Charge Pump for Oscillator Control
Original Publication Date: 1980-Jan-01
Included in the Prior Art Database: 2005-Feb-13
Phase lock loops implemented in integrated circuits have used so called differential charge pumps for enhancing phase lock loop operation. Such phase lock loops phase track input signals. During input signal loss, it is desired to maintain the output frequency in phase of the phase lock loop constant until return of the input signal. In a differential charge pump for the voltage controlled oscillator (VCO) in a phase lock loop being controlled, the current sources I3, I4 must bc balanced with the current sinks I1, I2 as well as with each other. Capacitors C1, C2 store the amplitude of the signal to be provided as an output to the oscillator via Q1, Q2.