| 摘要 |
<p>In a circuit configuration for the compensation of leakage currents in a voltage-controlled oscillator (12) of a PLL circuit (10), a control voltage is applied to the oscillator 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 (fref) 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 influence the frequency, 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 a voltage-follower-mode connected 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). <IMAGE></p> |
