公开(公告)号：WO1987004304A1

公开(公告)日：1987-07-16

申请号：PCT/US1986002714

申请日：1986-12-11

Applicant: MOTOROLA, INC.

Inventor： MOTOROLA, INC. ,  ENDERBY, Ralph, T. ,  FERRER, Enrique ,  SHEPHERD, Wayne, P.

IPC: H03B05/08

CPC classification number: H03L7/187 ,  H03B2201/0208 ,  H03L7/099 ,  H03L2207/06

Abstract: A variable capacitance circuit includes a varactor (20) having an anode side (22) and a cathode side (21). A first variable bias voltage is applied to one of the sides (21 or 22) and one of a plurality of voltages is applied as a second bias voltage to the other side (21 or 22) for controlling the capacitance of the varactor (20). A voltage multiplier circuit connected to a voltage divider network is used for supplying the plurality of voltages. A decoder (81) is responsive to input signals for selecting and applying one of the multiple voltage outputs. The variable capacitance circuit is used in a voltage control oscillator (11) of a frequency synthesizer for providing extended frequency range.