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Chapter: Electronic Devices - Special Semiconductor Devices

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Important Short Questions and Answers: Special Semiconductor Devices

Electronic Devices - Special Semiconductor Devices - Important Short Questions and Answers: Special Semiconductor Devices

SPECIAL SEMICONDUCTOR DEVICES

 

1.  What is a Thermistor?

 

Thermistor is a combination of thermal and resistance. A thermistor is a resistance with definite thermal characterisics. Thermistors are widely used for temperature compensation. ie cancelling the effect of temperature, liquid level, gas flow etc.

 

Thermistors are made in the shape of beads, probes, discs, washers etc.

2.  Explain Tunneling principle?

 

The tunnel diode is PN junction device, which operates in certain regions of its IV characteristics by the quantum mechanical tunneling of electrons through the potential barrier of the junction.The tunneling process for reverse current is essentially the zener effect, although negligible reverse bias is needed to initiate the process in tunnel diodes.It is also called Esaki diode.

 

3.  What is a tunnel diode?

 

The tunnel diode is a pn junction diode in which the impurity concentration is greatly increased about 1000 times higher than a conventional PN junction diode thus yielding a very thin depletion layer. This diode utilizes a phenomenon called tunneling and hence the diode is referred as tunnel diode.

 

4.   What the applications of Tunnel diode?

 

High speed switching circuits Logic circuits

 

5.     What is a schottky diode?

 

A special type of diode which is manufactured for high frequency (> 10 MHZ) rectifying action and for fast switching is called as schottky diode. It is formed by connecting a metal and a semiconductor along with the ohmic contacts.

 

6.     What are the other names of schottky diode?

·        Rectifying metal semiconductor diode

·        Surface barrier diodes.

·        Hot carrier diodes

7.     What are hot carriers?

 

The injected carrier from the semiconductor to the metal is termed as hot carriers. They are so called because they possess high kinetic energy.

 

8.  List some applications of zener diode.

 

Zener diode find wide commercial and industrial applications. Some of their common applications are:

 

·                    As voltage regulators.

·                    As peak clippers or voltage limiters.

·                    For wave shaping.

 

·                    For meter protection against damage from accidental application of excessive voltage.

 

As a fixed reference voltage in a network for biasing and comparison purposes and for calibrating voltmeters.

9.     Give the applications of schottky diode.

 

1. It can switch off faster than bipolar diodes

 

2. It is used to rectify very high frequency signals (>10 MHZ)

 

3.   as a switching device in digital computers.

 

4. It is used in clipping and clamping circuits.

 

5. It is used in communication systems such as frequency mixers, modulators and detectors.

 

10.                        Draw symbol of Varactor diode.


 


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