A voltage controlled oscillator (VCO)
is an oscillator where the principal variable or tuning element is a varactor diode.
The VCO is tuned across its band by a "clean" dc voltage applied to the
diode to vary the net capacitance applied to the tuned circuit.
VCOs are used in virtually all Spread Spectrum, RF and wireless systems. Every synthesizer
and PLL has at least one VCO in it thus designers should know something about them. Pick one of
the links below to find out more information about this important subject!