Physics of Semiconductor Devices

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Varactor - Exam January 27, 2012

A varactor is a pn junction that is used as a variable capacitor.

(a) How can a pn junction be used as a variable capacitor? How do you change the capacitance?

(b) What determines the depletion width at zero bias voltage?

(c) Draw the electric field in a varactor at zero bias voltage.

(d) How could you measure the doping concentration from the capacitance-voltage characteristics?