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Title:
CIRCUIT CONFIGURATION FOR COMPENSATION OF LEAKAGE CURRENTS IN A VOLTAGE-CONTROLLED OSCILLATOR OF PLL CIRCUIT
Document Type and Number:
Japanese Patent JP2002314412
Kind Code:
A
Abstract:

To provide a circuit configuration to compensate leakage currents in a voltage-controlled oscillator of a PLL circuit.

A control voltage is applied to the voltage controlled oscillator (12) by way of a loop filter (20), which is generated by a phase detector (16) as a function of the phase difference between the phase of a reference signal and the phase of the signal output by the voltage controlled oscillator (12). This oscillator (12) contains varicap diodes (28, 30), as circuit elements to which the control voltage is applied via a control line (34). A compensation circuit (K) is provided with varicap diodes (36, 38) in the same configuration as those in the oscillator (12), and an operational amplifier (40) with a differential output is provided which has an input (41) that is connected to the control line (34). It reproduces at one of its outputs (44) the control voltage which it applies to the varicap diodes (36, 38) in the compensation circuit (K). From its other output (46) it supplies a current equal to the leakage current of the varicap diodes (36, 38) in the compensation circuit (K). A current shunt-off branch leads from the control line (34), by way of which a current flows from the control line (34) which corresponds to the current supplied by the operational amplifier (40).


Inventors:
VANSELOW FRANK
CURRADI LEONARDO
Application Number:
JP2002055413A
Publication Date:
October 25, 2002
Filing Date:
March 01, 2002
Export Citation:
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Assignee:
TEXAS INSTRUMENTS DEUTSCHLAND
International Classes:
H03B5/04; H03B5/12; H03L7/099; H03B1/00; (IPC1-7): H03L7/099; H03B5/12
Attorney, Agent or Firm:
Akira Asamura (3 outside)



 
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