Varicap Diode Test

- February 12, 2019

The term varactor is originated from a variable capacitor. Using varactor diodes makes it possible to tune filters.

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Variable capacitance diodes operate using a reverse bias voltage applied to the p n junction of the diode.

Varicap diode test. If you have ever wanted to build or replace your transmitters variable frequency oscillator vfo with a voltage controlled oscillator vco but had no idea where to start then this small project should give you a couple of hints. Just hook the black lead to one leg and the red lead to the other. Although varactor diodes or varicap diodes can be used many different circuits they find uses in two main areas.

The varactor diode acts like a variable capacitor under reverse bias. Voltage controlled oscillators vcos. The measurements were performed for comparative purposes on the following types of diodes.

If it shows continuity 600 ohm 1k ohm on my 1k range the red lead is on the anode. Dut device under test is the led being evaluated. If it shows an open reverse the leads.

But i wondered about how ordinary diodes would perform in the place of the varicap diode. Varactor diode operates only in reverse bias. Voltage controlled oscillators are used in many different.

Fortunately varactor diodes behave just like any other diode on the diode test range of a multi meter. In particular if you want a large capacitance at the top of the range you need a diode with quite a large junction area. Testing and using varicap diodes variable capacitance diodes in vco oscillators.

The simple test circuit diagram of the set up is shown below. 8 rectifier diodes 2 small signal switching diodes 1 actual real and propoer varicap varactor diode. Varactor diodes are also termed as varicap diodes in fact these days they are usually termed as varactor diodeseven though the variable capacitance effect can be exhibited by the normal diodes p n junction diodes but varactor diodes are preferred for giving the desired capacitance changes as they are special types of diodes.

The only special thing about a varicap diode is that it is specially designed to make this effect as linear and good as possible. As this reverse bias voltage increases the depletion layer at the p n diode junction widens. Varactor diode is also sometimes referred to as varicap diode tuning diode variable reactance diode or variable capacitance diode.