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Types of Diodes

Updated on August 28, 2014

Diode

A diode is a semiconductor device which offer zero resistance to the flow of current when it is forward biased and infinite resistance the flow of current when it is reverse biased.

The most common function of a diode is to allow an electric current to pass in one direction. This unidirectional behavior is called rectification. It is used to convert alternating current to direct current.

The different types of diodes. Of which the most popular types of diodes are the followings:

  1. Zener diodes
  2. Schottky diodes
  3. Avalanche diodes
  4. Veractor diodes
  5. Tunnel diodes
  6. IMPATT diodes
  7. Gunn diodes
  8. LEDs
  9. LASER Diode
  10. PIN DIODE
  11. Photo diodes

Symbol

Zener diode

Zener Diode

The Zener diode was invented by Clarence Melvin Zener of Carnegie Mellon University after whom the zener diode was named so. The zener diode has the property of conducting in the backward direction when the voltage crosses the breakdown voltage. Whereas in the case of ordinary PN junction diode, the current through the junction and the power dissipated at the junction will be high. This increases the chances for damage of diode. This can be overcome using the Zener diode.

Applications of zener diode

  1. Zener Regulators
  2. Zener Controlled Comparators
  3. Zener Limiters
  4. Role in Power Supplies

Schottky - Diode

Schottky - Diode is an ordinary semiconductor pn - diode in which the p-layer consists of metal and the n-layer of a semiconductor material (SiC, GaAs, SiGe). It has the following advantages.

  • low turn-on voltage
  • fast recover time
  • low junction capacitance

Applications

  1. Power rectifier
  2. RF mixer and detector diode
  3. Voltage clamping
  4. Reverse current and discharge protection
  5. Power supply
  6. Solar cell applications

Avalanche Diode

Avalanche Diode

These diodes are similar to that of the Zenar diodes that conduct in the reverse direction when the reverse bias voltage exceeds the breakdown voltage. The difference between the avalanche diode and the Zenar is that the channel length. The only practical difference is that the two types have temperature coefficients of opposite polarities.

Symbol of VERACTOR DIODE

Veractor Diode

The Veractor Diode is normally called as voltage variable capacitor. It is also called as Varicap diode. Is is normally operated in reverse biased state. No current can flow through it during reverse bias. The capacitance is varied by varying the applied bias voltage. The thickness of the depletion region is proportional to the square root of the applied voltage and the capacitance is inversely proportional to the depletion region thickness. And hence the capacitance is inversely proportional to the square root of applied voltage.

Applications

  1. used as voltage-controlled capacitors
  2. They are commonly used in voltage-controlled oscillators, parametric amplifiers, and frequency multipliers

Tunnel Diode

The Tunnel or Esaki diode is a diode which possess negative resistance. It is said so because the current decreases with increased forward voltage. The Tunnel diode uses semiconductor materials that are lightly doped with one impurity atom for ten-million semiconductor atoms. This low doping level results in a relatively wide depletion region.


Applications

  1. They are used in low power amplifiers.
  2. Since they are more resistant to nuclear radiation, tunnel diodes are used in space applications like amplifiers for satellite communications.

Impatt Diode

Impatt Diode

IMPATT diode is a high frequency device that operates at or above microwave frequencies. It has an ability to operate at frequencies between about 3 and 100 GHz or more. An alternating signal is generated simply by applying a DC supply when there is a suitable tuned circuit. Voltage higher than 70V is required for the working of IMPATT diode. Since avalanche is a noisy Process, It is very noisy.

Applications

  1. This diodes are used as microwave oscillators
  2. Negative resistance amplification.
  3. used in alarm n/w, police Radar and low power microwave transmitter
  4. useful in FM Telecommunication transmitters and cw dopper radar transmitter.

Gunn Diode

Gunn Diode

A Gunn diode is used in high-frequency electronics. It is also known as a transferred electron device (TED). There are three regions in Gunn diode. They are

1. two heavily doped N region on each terminal

2. and thin layer of lightly doped material in between

When a voltage is applied, the electrical gradient across the thin middle layer will be the largest. It acts as a normal conductor. But when the voltage increases the conductive properties of the middle layer will be altered. There will be increase in its resistivity, preventing further conduction and current starts to fall.

Applications

  1. Its largest use is in electronic oscillators to generate microwaves
  2. used in radar speed guns and microwave relay transmitters.

A Gunn diode is used in high-frequency electronics. It isalso known as a transferred electron device (TED). There are three regions in Gunn diode. They are

1.two heavily doped N region on each terminal

2.and thin layer of lightly doped material in between

When a voltage is applied, the electrical gradient across the thin middle layer will be the largest. It acts as a normal conductor. But when the voltage increases the conductive properties of the middle layer will be altered. There will be increase in its resistivity, preventing further conduction and current starts to fall.

Light Emitting Diode

Light Emitting Diode

A light-emitting diode (LED) is a PN junction diode which emits visible light when forward biased. When forward biased the electrons in it combines with the holes giving out energy in the form of photons. The color of the emitted light is determined by the energy band gap of the semiconductor.

Applications

  1. Light-emitting diodes are used in applications as diverse as aviation lighting, automotive lighting, advertising, general lighting, and traffic signals.
  2. Infrared LEDs are also used in the remote control units of many commercial products including televisions, DVD players and other domestic appliances.
  3. LEDs are also used in seven-segment display.

Laser Diode

A laser diode is similar to light-emitting diode. The electrons in it combines with the holes giving out energy in the form of photons. A laser diode is formed by doping a very thin layer on the surface of a crystal wafer. The crystal is doped to produce an n-type region and a p-type region


Applications

  • Pumping of solid-state and fiber lasers
  • Material processing (welding of plastic materials, soldering and annealing of metals)
  • Medical equipment (hair removal, surgery, dentistry and ophthalmology)
  • Lighting
  • Measuring equipment
  • Printing industry
  • Science and research

PIN diode

Pin Diode

PIN diode is formed of N and P regions and an intrinsic layer (I region) is sandwiched between them to form the PIN structure. The presence of intrinsic layer increases the resistance. This make it unsuited for rectification applications. The high resistivity decrease in capacitance between P and N regions as it is inversely proportional to the separation between these regions. It allows a faster response for the diode.

Applications

  1. It is used as a switching diode for signal frequencies up to GHz range
  2. As an AM modulator of very high frequency signals.

Symbol of Photo Diode

Photo diode

Photo diode

Photo diode is a type of PN junction diode which converts light energy into electrical energy. It is capable of converting light into either current or voltage, depending upon the mode of operation. When a photon of sufficient energy strikes the Photo diode, it emits an electron and creates a free electron and a positively charged hole. The output voltage or current of the device depends on the intensity of light falling on it.

Applications

  1. P-N photo diodes are used in similar applications to other photo detectors
  2. Photo diodes are used in consumer electronics devices such as compact disc players, smoke detectors, and the receivers for infrared
  3. Photo diodes are often used for accurate measurement of light intensity in science and industry.
  4. They are also widely used in various medical applications, such as detectors for computed tomography and pulse oximeters.
  5. used in fiber optic communication.



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    • dilipchandra12 profile image

      Dilip Chandra 3 years ago from India

      A useful info, bookmarking this hub for future ref... Thank you for sharing.

    • Jivil George profile image

      Jivil George 3 years ago from India

      easy to understand, good one

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