What is the use of varactor diode in FM receiver?

What is the use of varactor diode in FM receiver?

Varactor or varicap diodes are used mainly in radio frequency or RF circuits to provide voltage controlled variable capacitance. These electronic componenta can be used in a whole variety of ways where a capacitance level needs to be controlled by a voltage.

How do you use a varactor diode?

Generally the use of a varicap diode in a circuit requires connecting it to a tuned circuit, usually in parallel with any existing capacitance or inductance. A DC voltage is applied as reverse bias across the varicap to alter its capacitance. The DC bias voltage must be blocked from entering the tuned circuit.

What is purpose of varactor diode?

A varactor diode is a simple variable capacitor that allows oscillator circuits and other circuits to be easily tuned by applying a voltage. These diodes have a similar structure as a p-n diode; the structure of a varactor diode is rather simple and illustrates its power as a component with nonlinear reactance.

How does the varactor diode act as a variable capacitor give the relation equation between its junction capacitance and reverse bias voltage?

Operation of Varactor Diode The junction capacitance of a p-n junction diode is inversely proportional to the width of the depletion layer. It causes the width of the depletion layer to decrease, resulting in higher capacitance. Similarly, increasing the reverse bias voltage should decrease the capacitance.

Why is varactor diode often made by epitaxial growth technique?

Varactor diode manufacturers typically use an epitaxial structure to minimise this resistance. When designing the circuit, the Q of the circuit can be maximised by minimising the capacitance. These are the main varactor specifications that need to be considered outside the basic diode specifications.

Which is the principal characteristic of a varactor diode?

The V-I characteristics of the diode are non-linear and it permits the flow of current in only one direction In forward bias mode, the diode allows the flow of current and offers very low resistance. Likewise, in the reverse bias mode, the diode blocks the current flow and offers very high resistance.

What is varactor diode modulator?

Varactor diode modulator is the direct method of FM generation wherein the carrier frequency is directly varied by the modulating signal. A varactor diode is a semiconductor diode whose junction capacitance varies linearly with applied voltage when the diode is reverse biased. for generation of FM wave.

What is a varactor diode symbol of varactor diode?

Symbol of Varactor Diode The symbol of the varactor diode is similar to that of the PN-junction diode. The diode has two terminals namely anode and cathode. The one end of a symbol consists the diode, and their other end has two parallel lines that represent the conductive plates of the capacitor.

How does the varactor diode act as a variable capacitor?

What is a Varactor Diode? A Varactor Diode (also known with the names Varicap Diode, Varactor Diode, Tuning Diode) is a p-n junction diode which acts as a variable capacitor under varying reverse bias voltage across its terminals.

What is varactor diode and where it is used?

Varactor diodes are used in electronic tuning systems to eliminate the need for moving parts. Varactor [also called varicap, variable reactance diode, or tuning diode] diodes are the semiconductor, voltage-dependent, variable capacitors.

What are the important specifications of varactor diode?

Understanding Varactor Diode Specifications: specs & parameters

• Varactor reverse breakdown specification.
• Varactor diode reverse current specification.
• Capacitance range and capacitance ratio specification.
• Maximum frequency of operation specification.
• Varactor Q specification.

How are varactor diodes used in phase modulators?

Frequency & phase modulators: Varactor diodes can be used in frequency and phase modulators. In frequency modulators they can be placed across the resonant element within the generator and the audio applied to the diode.

How are varactor diodes used in RF filters?

The varactor diode is a key component within the voltage controlled oscillator. RF filters: Using varactor diodes makes it possible to tune filters. Tracking filters may be needed in receiver front end circuits where they enable the filters to track the incoming received signal frequency.

Which is a property of the varactor diode?

An important property of the varactor diode that operates in reverse biased condition, and the RFC choke is a radio frequency choke whose reactance is high at the carrier frequency to prevent the carrier signal from getting into the modulator signal circuit.

Can a varactor diode be used in reverse bias?

Varactor diode can only be operated in reverse bias. It acts like variable capacitance in reverse bias operation. Varactor Diode is also known as Tuning Diode, Variable Reactance Diode, Varicap Diode or variable capacitance diode.