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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