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varactor diodes


Kevin Weddle

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Does a varactor diode release any stored energy when the voltge is removed, like a capacitor or inductor does?

A varactor diode has a very low capacitance of 2pF for ones used to tune very high frequencies to about 200pf to tune AM broadcast band radios. This is an extremely small amount of capacitance that can hold a charge because the diode is reverse-biased and therefore does not conduct but the charge cannot power anything.
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A 200pF capacitor can discharge relatively slow with a large resistance.

22M is the highest resistor value in my collection. 200pf discharges completely (5 time-constants) by one in only 22 milli-seconds. That is not slow.
You can make the discharge faster by increasing the reverse bias voltage to reduce the capacitance value.
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