Diode and it's types with symbol.

In this content, you can learn about introduction of Diode and it's type and it's symbol.

 DIODE

A diode is a semiconductor device which is made by P-type and N-type Semiconductor material. It is a unidirectional device which allow to flow of current in one direction I.e. anode to cathode but do not allow to flow of current from cathode to anode terminals.

              Generally a diode consists one pn-junction. Usually diodes are used in rectification, voltage regulation, light generation (emission), conversion for light energy into electrical energy etc. Diode are smaller in size, cheaper, robust and easily available. 

There are different types of diode such as pn-junction diode, zener diode, varactor diode, light emitting diode (LED), photo-diode etc.

  Types of diode

(1) Pn-junction Diode

Pn-junction Diode is two layer and two terminal, semiconductor device. It is made by P-type and N-type semiconductor material and it consists one pn-junction. It's two terminals are anode and cathode. 

A pn-junction diode is an unidirectional device which is mainly used for rectification (ac to dc conversion). It is a non- linear device. Pn-junction Diode are smaller in size, cheaper, robust and have higher operating efficiency.

Circuit symbol of diode:-

Figure 1.2 shows the schematic symbol of pn-junction diode. In this symbol arrow indicates the direction of flow of current and a terminal is connected with it is called anode.

 Generally anode terminal is represented by positive polarity (+). A terminal is connected with" bar" is called cathode and generally cathode terminal is represented by negative polarity (–).

 

(2) Zener Diode:-

The zener diode is a PN- junction device and it always operates in the reverse break down reason. The zener diode is also known as breakdown diode or voltage regulator diode. It is always operated in reverse bias.

 The zener diode is fabricated by silicon because of higher operating temperature and current capability of silicon. The knee point is also more sharp in case of a silicon diode. A zener diode is used in a voltage regulator circuit in reverse bias condition. In reverse bias, it is popularly known as constant voltage device.

Circuit symbol of Zener Diode

Fig 1.6 shows that circuit symbol of Zener Diode.

(3) Power Diode:-

A power diode is also pn-junction device but it's voltage, current and power rating is high. It is also known as high power diode. It have capacity to carry a very high current and withstand at very high voltage. The construction of power diode is different from low signal pn-junction diode. 

The power diode is used in power electronics circuit. The power diodes are now available with forward current rating of 1A to several thousand amperes and the voltage rating of 50 V to 5000 V or more.

Circuit symbol of power diode

Figure 1.10 shows that the circuit symbol of power diode. The circuit symbol of power diode similar to low signal pn-junction diode.

(4) Varactor Diode:-

Varactor Diode is a semiconductor, voltage dependent, variable capacitor diode. In other word it is defined as" a junction diode which acts as a variable capacitor under changing reverse biase is known as a varactor diode".

 The varactor diodes are always operated in reverse biase. A varactor diode is specially constructed to have high capacitance under reverse biase.

Circuit symbol of varactor diode:-

Figure 1.14 shows the symbol of varactor diode.

(5) Light Emitting Diode ( LEDS):-

Light emitting diode is pn-junction diode that emits light when activated. It is two lead semiconductor light source. LEDS produces either invisible infrared light or visible light of different colour. The light of different colour which is produced by LEDs are Red, Yellow, Orange, Green, White, Blue and Amber.

  LED is always operated in forward biase. In reverse biase LED do not produce light ( Visible or invisible). LEDs are fabricated with" direct band gap" semiconductor material and these semiconductor materials are gallium arsenide ( GaAs), gallium arsenide phosphide ( Ga As P) or gallium phosphide (Gap). The typical value of cut- in voltage is 1-3 V of a LED diode.

Circuit symbol of Light Emitting Diode ( LEDs):-

Figure 1.57 shows the symbol of light emitting diode.

(6) Photo Diode:-

A photo diode is a semiconductor device that converts light into an electrical current. It consumes light energy to generate electric current. It is also known as photo-detector, photo- Sensor or light- detector device.

  Photo-diode are specially designed to operate in reverse biase condition. Photo diode is very sensitive to light so when light or photo falls on the photodiode it is easily convert light into electric current. 

     The construction and working of photo diode is almost similar to the normal pn-junction diode. The photo diode is constructed by photo sensitive materials namely CDs, Se, zinc sulphide and Si.

Circuit symbol of photo diode:-

Figure 1.50 shows the symbol of photo diode.

Conclusion:-

You have learnt about introduction of diode and it's type and it's symbol.