Type of Diode - Simple
Introduction
Diodes
are electronic components functions as a one-way valve it means it allow
current to flow in one direction. These diodes are manufactured by the
semiconductor
materials germanium, silicon and selenium. Operation of diode can
be classified in two
ways, if it allows the current then it is forward biased
otherwise it is reverse biased.
1. Small Signal
Diode
It
is a small device with disproportional characteristics and whose applications
are
mainly involved at high frequency and very low currents devices such as
radios and
televisions etc. To protect the diode from contamination it is
enveloped with a glass so
it is also named as Glass Passivated Diode which is
extensively used as 1N4148.
The
appearance of signal diode is very small when compared with the power diode. To
indicate the cathode terminal one edge is marked with black or red in color.
For the
applications at high frequencies the performance of the small signal
diode is very
effective.
With
respect to the functional frequencies of the signal diode the carrying capacity
of
the current and power are very low which are maximum nearly at 150mA and
500mW.
The
signal diode is a silicon doped semiconductor diode or a germanium doped diode
but depending up on the doping material the characteristics of the diode
varies. In
signal diode the characteristics of the silicon doped diode is
approximately opposite
to the germanium doped diode.
The silicon signal diode has high voltage drop
at the coupling about 0.6 to 0.7 volts so, it has very
high resistance but low
forward resistance. On other hand germanium signal diode has low resistance
due
to low voltage drop nearly at 0.2 to 0.3 volts and high forward resistance. Due
to small signal the
2. Large Signal Diode
These diodes have large
PN junction layer. Thus the transformation of AC to DC
voltages is unbounded.
This also increases the current forward capacity and reverse
blocking voltage.
These large signals will disrupt the functional point also. Due to
this it is
not suitable for high frequency applications.
The main applications of
these diodes are in battery charging devices like inverters.
In these diodes
the range of forward resistance is in Ohms and the reverse blocking
resistance
is in mega Ohms. Since it has high current and voltage performance these
can be
used in electrical devices which are used to suppress high peak voltages.
3. Zener Diode
It
is a passive element works under the principle of zener breakdown.
First
produced by Clarence zener in 1934.It is similar to normal diode in forward
direction, it also allows
current in reverse direction when the applied voltage
reaches the breakdown voltage.
It is designed to prevent the other
semiconductor devices from momentary voltage
4.
Light Emitting Diode (LED)
These
diodes convert the electrical energy in to light energy.
First production
started in 1968. It undergoes electroluminescence process in which
holes and
electrons are recombined to produce energy in the form of light in forward
bias
condition.
Earlier
they used in inductor lamps but now in recent applications they are using in
environmental and task handling. Mostly used in applications like aviation
lighting,
traffic signals, camera flashes.
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5.
Constant Current Diodes
It
is also known as current-regulating diode or constant current diode or
current-
limiting diode or diode-connected transistor. The function of the diode
is regulating
the voltage at a particular current.
It
functions as a two terminal current limiter. In this JFET acts as current
limiter to
achieve high output impedance. The constant current diode symbol is
shown below.
TYPES OF MIC WATCH FULL
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