Mechanically controlled variable capacitors allow the plate spacing to be adjusted, for example by rotating or sliding a set of movable plates into alignment with a set of stationary plates. Low cost variable capacitors squeeze together alternating layers of aluminum and plastic with a screw. Electrical control of capacitance is achievable with varactors (or varicaps), which are reverse-biased semiconductor diodes whose depletion region width varies with applied voltage. They are used in phase-locked loops, amongst other applications. COUNT 5
QSN1 What do mechanically controlled variable capacitors enable to be modified? ANS1 the plate spacing QSN2 How do cheap variable capacitors vary the separation distance between layers of a plastic and aluminum? ANS2 with a screw QSN3 Of what type of diodes are varactors or varicaps comprised? ANS3 reverse-biased semiconductor diodes QSN4 What varies as a function of voltage in varactors? ANS4 depletion region QSN5 What is an application of varactors? ANS5 phase-locked loops