Editing Variable-frequency oscillator (section)

====Varactor====
{{see also|varactor|voltage controlled oscillator}}

A reversed-biased [[semiconductor]] [[diode]] exhibits capacitance. Since the width of its non-conducting [[depletion region]] depends on the magnitude of the reverse bias voltage, this [[voltage]] can be used to control the junction capacitance. The varactor bias voltage may be generated in a number of ways and there may need to be no significant moving parts in the final design.<ref name="Holt78">{{citation | last=Holt | first=Charles | title=Electronic Circuits | publisher=John Wiley & Sons | year=1978 | isbn=0-471-02313-2 }}</ref>
Varactors have a number of disadvantages including temperature drift and aging, electronic noise, low [[Q factor]] and non-linearity.