Charge-pump circuit for use in phase locked loop

Details Charge-pump circuit for use in phase locked loop Charge-pump circuit for use in phase locked loop

1994-04-05

1995-01-17

Grimm, Siegfried H.

Oscillators

Automatic frequency stabilization using a phase or frequency...

Transistorized controls

331 17, 331 25, 327157, 327159, H03L 7089, H03L 7093

Patent

active

053829239

ABSTRACT:
A charge-pump circuit for controlling a voltage controlled oscillator by converting a phase difference between two input signals, which never become low at the same time, into a voltage. The charge-pump circuit includes first and second feeder circuits, made of bipolar transistors, outputting current in accordance with the input signals; a capacitor circuit having first, second, and third capacitors, and the first and the second or the first and the third capacitors are charged by the output current from the first or the second feeder circuit; and a differential amplifying circuit amplifying the voltage between the ends of the first capacitor to a predetermined voltage for output. The differential amplifying circuit operates to draw the same leakage current from the second and the third capacitors when the first capacitor is not being charged. The charge-pump circuit is effectively used to control the frequency of the voltage controlled oscillator in an PLL circuit having a phase comparator, a voltage controlled oscillator, and an output circuit.

REFERENCES:
patent: 4959618 (1990-09-01), Shier

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