NE-502 varactor tuning input circuit

Published:2011/6/19 5:09:00 Author:John | Keyword: varactor, tuning input | From:SeekIC

The following figure is a tuning input circuit which achieves tuning function by variable voltage capacitance diode (varactor). The total tuning capacitance in parallel consists of adjusting capacitanc C1, fixed capacitanc C2 and varactor diode’s junction capacitance D1. The total tuning capacitance is connected with transformer secondary coil L2 in order to form the resonant circuit. In order to reduce the impact of the series combination of capacitor C3/CD1, setting value of capacitor C3 is usually larger than that of the diode. In other cases, in order to make the diode capacitance become a part of resonant circuit’s capacitor, the value of capacitor C3 is very close to that of the diode.



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