There are two types of FM modulators - direct and indirect. Direct FM capacitance of such a diode varies with applied voltage. A varactor diode is specifically. Varactor Diode Modulator is a semi-conductor diode having a variable junction capacitance. The variation is achieved by applying a reverse. Fig (b) shows the basic concept of a varactor frequency modulator. The L1 and C1 represent the tuned circuit of the carrier oscillator. Varactor diode D1 is.


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The modulating voltage which is in series with the varactor diode varactor diode modulator vary the bias and hence the junction capacitance, resulting the oscillator frequency to change accordingly. The external modulating AF voltage adds to and subtracts from the dc bias, which changes the capacitance of the diode and thus the frequency of oscillation.

Varactor FM Modulator

Positive alternations of the modulating signal increase the reverse bias on the varactor diode, which decreases its capacitance and varactor diode modulator the frequency of oscillation. All diodes exhibit this variable junction capacitance, but varactors are manufactured to exploit the effect and increase the capacitance variation.


The figure shows an example of a cross section of a varactor with the depletion layer formed varactor diode modulator a p—n junction. This depletion layer can also be made of a MOS or a Schottky diode. Varactor diode modulator in a circuit[ edit ] Tuning circuits[ edit ] Generally the use of a varicap diode in a circuit requires connecting it to a tuned circuitusually in parallel with any existing capacitance or inductance.

What is Varactor Diode? Working and Characteristics

The DC bias voltage must be blocked from entering the tuned circuit. Sometimes, with very high-Q tuned circuits, an inductor is placed varactor diode modulator series with the resistor to increase the source impedance of the control voltage so as not to load the tuned circuit and decrease its Q.

Another common configuration uses two back-to-back anode to anode varicap diodes. See lower left circuit in diagram.

The second varicap effectively replaces the blocking capacitor in the first circuit. This reduces the overall capacitance and the capacitance range by half, but has the advantage of reducing the AC component of voltage across each device and varactor diode modulator symmetrical distortion should the AC component possess enough amplitude to bias the varicaps into forward conduction.


A third circuit, at top right in diagram, uses two series-connected varicaps and separate DC and AC signal ground connections. The DC ground is shown as a traditional ground symbol, and the AC varactor diode modulator as an open triangle.

Here, in this article let us discuss in detail about the varactor diode circuit working and characteristics. What is a Varactor Diode?

Varactor Diode The varactor diode was named because of the variable reactor or variable reactance or variable capacitor or variable capacitance property of these varactor diode modulator. A varactor diode modulator diode is considered as a special type of diode that is widely used in the electronics industry and is used in various electronics applications.

Varactor diode is also a semiconductor microwave solid-state device, it is frequently used in applications where variable capacitance is desired which can be achieved by controlling voltage.

Varactor Diode Modulator

Varactor Diode Basics Varactor diodes are also termed as varicap diodes, in fact, these days they are usually termed as varactor diodes. Even though the variable capacitance effect can be exhibited by the normal diodes P-N junction diodesbut, varactor diodes are preferred for giving the desired capacitance changes varactor diode modulator they are special types of diodes.

These diodes are specially manufactured and optimized such that they enables a very high range of changes in capacitance.

Varactor diodes are again classified into various types based on the varactor diode junction varactor diode modulator.


And, these are termed as abrupt varactor diodes, gallium-arsenide varactor diodes, and hyperabrupt varactor diodes. Varactor Diode Symbol The symbol of varactor diode is shown in the figure. The varactor diode symbol consists of the varactor diode modulator symbol at one end of the diode that represents the variable capacitor characteristics varactor diode modulator the varactor diodes.

Varicap - Wikipedia

Varactor Diode Symbol In general, it looks like a normal PN- junction diode in which one terminal varactor diode modulator termed as the cathode and the other terminal is termed as anode.

This is a special design characteristic of the varactor diode. The varactor must not be forward biased because it cannot varactor diode modulator much current flow.