Types of Diode and Diode Applications

The diode is a two-terminal electronic component made up of semiconductor materials such as silicon, gallium, etc. It is a unidirectional device i.e. it allows current flow only in one direction. A diode is an uncontrolled device. There are different types of diode.

The internal resistance of an ideal diode is considered as zero in the forward biased condition and infinite in the reverse biased condition. In an electric circuit, a diode acts as a valve that directs the flow of current. According to the connection of the diode with the supply, the diode decides the path of the current to flow. In forward biased condition, the diode allows the current to flow through the low resistance path, whereas it provides the high resistance path to flow in the case of the reverse biased condition.

Depending on the construction, operation, characteristics of the diodes, the diodes are classified into many types.

Diode and its types

The types of diode are

  1. Avalanche Diode
  2. Constant Current Diode
  3. Gunn Diode
  4. Large Signal Diode
  5. Laser Diode
  6. Light Emitting Diode (LED)
  7. Photodiode
  8. PIN Diode
  9. PN Junction Diode
  10. Schottky Diode
  11. Shockley Diode
  12. Small Signal Diode
  13. Step Recovery Diode
  14. Tunnel Diode
  15. Vacuum Diode
  16. Varactor Diode
  17. Zener Diode

Avalanche diode

Avalanche diode is a PN junction diode that gives a high reverse voltage current. This diode works on the reverse biased condition and as the avalanche breakdown voltage occurs, the diode current increases rapidly.

The diode protects the circuit components from high current damages and is used in the production of microwave frequency generation and radiofrequency noise production.

You can read more about avalanche diode here.

Constant current diode

A constant current diode is a diode that allows a constant current in the circuit. It is also known as a current-limiting diode or a current-regulating diode. This diode regulates the voltage at the constant current.

Gunn diode

Gunn diode is made up of only N-type semiconductor materials. It has a very thin depletion region between two N-type semiconductors. The diode exhibits negative resistance as the current decreases exponentially after a certain voltage. But before that, the current and voltage increase proportionally.

Large signal diode

The PN junction layer present in the large signal diode is large. This results in the unbounded transformation of AC to DC voltages. The forward current capacity increases in the diode and the functional point is disrupted. This diode is used in appliances such as inverters, but not suitable to use in high-frequency devices.

LASER diode

It is a PN junction diode that has an active intrinsic region between the junction. It is used in fiber optic communications and laser printing. The diode has many types such as double heterostructure laser, quantum well laser, quantum cascade laser, etc.

Light emitting diode (LED)

The light-emitting diode involves the conversion of electrical energy to light energy. The recombination of the holes and the electrons present in the semiconductor material produces energy. The diode operates in the forward biased condition. In traffic signals, these diodes are used widely.

You can read more about Light emitting diode (LED) here.


It is a semiconductor diode that converts light into electrical energy. When light falls on the surface of the diode, the electrons get excited and they move. Their movement causes current to flow in the diode.

PIN diode

The PIN diode is a modified and upgraded version of a normal PN junction diode. It has an intrinsic semiconductor layer in between the P-type and N-type semiconductor materials of the diode.

The use of the intrinsic layer increases the area of the depletion region in the diode. This type of diode is used in attenuators and photodetectors.

You can read more about PIN diode here.

PN junction diode

PN junction diode is made up of P-type and N-type semiconductor material which conducts current in the forward biased condition. When the diode is reverse biased, it acts as an open circuit and does not conducts. This is the simplest form of a diode.

Schottky diode

The diode is made up of only N-type semiconductor materials. The metals such as gold, platinum are used as the anode terminal of the Schottky diode. There is no formation of depletion layer inside the diode, hence the switching of the diode is fast and it increases the efficiency. The voltage drop in this diode is comparatively low.

You can read more about schottky diode here.

Shockley diode

It is a four-layered semiconductor diode named as PNPN diode. The Shockley diode acts as a thyristor having no gate terminal. The input of the diode is the forward voltage. This diode can be used in SCR as trigger switches.

You can read more about shockley diode here.

Small signal diode

This is a small-sized diode that has a marked cathode terminal. The small-signal diode is used in the devices involved in high frequency and low current operations. Due to the presence of small signals, the functional point is not disrupted.

Step recovery diode

The step recovery diode is the diode that can store charges of the positive pulses. The stored charges are then used in the negative pulse of the sinusoidal signals. The diode is also known as a snap-off diode as the rise time of the current pulse is the same as the snap time.

This diode is used in multipliers of higher-order and the circuits used as a pulse shaper. The cut-off frequency of the diode is very high and has a great efficiency for the multipliers of lower order.

Tunnel diode

The tunnel diode is a device that can be turned on electrically as well as mechanically. The concentration of the dopants in this diode is very high.

The tunnel diode is used as a high-speed switch in oscillators and amplifiers as it exhibits a tunneling effect. This diode is a negative conductance device.

You can read more about tunnel diode here.

Vacuum diode

The diode has electrodes that act as anode and the cathode terminals of the diode. This diode has high electron emission capacities. The diode behaves like a switch and conducts when the anode is positive to the cathode terminal.

Varactor diode

The varactor diode has a capacitance effect as it has two parallel plates that store charges. The diode operates in reverse biased condition only. It is also known as a vertical diode. The diode is mainly used in parametric amplifiers and voltage-controlled oscillators.

You can read more about varactor diode here.

Zener diode

A Zener diode is made up of PN junction semiconductor materials. The diode mainly operates in the reverse biased region. At the reverse breakdown voltage, the current increases sharply. In the forward biased condition, the diode behaves just like a normal semiconductor diode.


Sunmoni Gohain
NIT Silchar

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