Semiconductor Electronics: Materials, Devices and Simple Circuits


The diode is our first semiconductor gadget. The diodes distinctive component is that it conducts current in one way, however, not the other.



What is a Diode?

A diode is a two-terminal electronic segment that conducts current principally one-way or asymmetric conductance. It has low ideally zero obstruction in one direction and high i.e. preferably boundless opposition in the other. A diode vacuum tube or thermionic diode is a vacuum tube with two terminals.

It has a warmed cathode and a plate, where electrons can stream just a single way, from cathode to plate. A semiconductor diode is most regularly in use today. It is a translucent bit of semiconductor material with a p–n intersection associated with two electrical terminals. Semiconductor diodes were the main semiconductor electronic gadgets.

The disclosure of topsy-turvy electrical conduction over the contact between a glasslike mineral and a metal. It was made by German physicist Ferdinand Braun in 1874. Today, most diodes are made of silicon, however other semiconducting materials. For example, gallium arsenide and germanium are likewise useful.

Diode Construction and Symbol

A standard diode is presented as a triangle bordering the line. The terminal entering the level edge of the triangle speaks to the anode and the opposite end the cathode. The current consistently move from anode to cathode, yet never the other route round.

Diodes can be made of both of the two semiconductor materials, silicon and germanium. At the point when the anode voltage is surer than the cathode voltage. The diode is supposed to be forward-one-sided and it leads promptly with a moderately low-voltage drop. Moreover, when the cathode voltage is more certain than the anode, the diode is supposed to be opposite one-sided. The bolt in the diode speaks to the heading of the regular current stream when the diode conducts.

Diode Characteristics

1)Forward-biased Diode

At the point when the voltage is applied in the opposite way over the diode. The depletion region starts to contract. In a reverse-biased diode, the electrons and holes would be pulled away from the intersection. However, a forward-one-sided situation guarantees that the electrons and holes push toward the intersection. ‘

As they are repulse from the positive and negative terminals of the voltage source individually. Given an incredible enough applied voltage, both the holes and the electrons would conquer the exhaustion district and meet close to the intersection. Here they could join in a constant cycle, shutting the circuit and permitting the current stream.

For silicon diode, the forward voltage is 690mV. For germanium, it is 300mV forward voltage. The possible energy over the p-type material is positive and over the n-type material, the likely energy is negative.

2)Reverse Bias

If a voltage is applied over the diode. The n-type half of the diode is associated with the positive terminal of the voltage source. The p-type half is associated with the negative terminal. Electrons from the outer circuit would make more negative particles in the p-type district by “filling the holes”.

Certain particles would be made in the n-type area as electrons are uprooted toward the positive terminal of the voltage source. Subsequently, the consumption district would increment and the voltage between the p-type and n-type locales would likewise increment as the all-out charge on each side. The intersection increments in greatness until the voltage over the diode rises and contradicts the applied voltage and counterbalances it, stopping the current through the circuit.

This cycle happens almost immediately and brings about basically no current move through the circuit when voltage is applied toward this path over the diode. This is a reverse-biased p-n junction. For silicon diode, the opposite voltage is – 20μA and for germanium, – 50μA is the reverse voltage. The expected energy over the p-type material is negative and over the n-type material, the likely energy is positive.

3)Zero-biased Diode

Zero biased PN Junction diode is a diode with no Bias mode. Without applying any voltage (forward or invert) over its terminals are supposed to be in Equilibrium mode (Zero inclination mode).

Types of Diodes

  1. Light Emitting Diode
  2. Laser diode
  3. Avalanche diode
  4. Zener diode
  5. Schottky diode
  6. Photodiode

Light Emitting Diode (LED)

At the point when electric current flows between the terminals go through this diode, light is created. As such, light is produced when an adequate measure of sending current goes through it. In numerous diodes, this light created isn’t noticeable as they are recurrence levels that don’t permit perceivability. LEDs are accessible in various shadings. There are tricolor LEDs that can transmit three tones all at once. Light tone relies upon the energy hole of the semiconductor utilized.

Laser Diode

It is a different kind of diode as it produces coherent light. It is exceptionally utilized in CD drives, DVDs and laser gadgets. These are exorbitant when contrasted with LEDs and are less expensive when contrasted with other laser generators. Restricted life is the main disadvantage of these diodes.

Avalanche Diode

This diode has a place with a reverse predisposition type and works utilizing the torrential slide impact. At the point when a voltage drop is consistent and is autonomous of current, the breakdown of torrential slide happens. They display significant levels of affectability and subsequently utilized for photo identification.

Zener Diode

It is the most valuable sort of diode as it can give a steady reference voltage. These are worked backward predisposition and separate on the appearance of a specific voltage. In the event that current going through the resistor is restricted, a steady voltage is created. Zener diodes are generally useful in power supplies to give a reference voltage.

Schottky Diode

It has a lower forward voltage than other silicon PN diodes. The drop will be visible where there is low current and at that stage, voltage ranges somewhere in the range of 0.15 and 0.4 volts. These are built contrastingly to get that exhibition. Schottky diodes are exceptionally in use in rectifier applications.


A photo-diode can distinguish even a modest quantity of current stream that comes because of the light. These are useful in the location of the light. This is a converse inclination diode and utilized in sun-powered cells and a photometer. They are even useful to produce power.

FAQs about Diode

Q.1. What are the applications of diode?

Answer: Followings are the applications and uses of the diode:

  • In the clipping circuit
  • In clamping circuits
  • As a rectifier
  • In logical gates
  • In reverse current protection

Q.2. What is the breakdown voltage of the diode?

Answer: The breakdown voltage of a diode is the base opposite voltage applied to make the diode breakdown. This leads the diode conduct in the reverse direction. If a sufficient electric field is applied, all insulators become conveyors or conductors. On the off chance that the voltage applied over a bit of it expands. At a specific electric field, the quantity of charge transporters in the material out of nowhere builds tremendously and its resistivity drops, making a solid flow move through it. This is an electrical breakdown.

Breakdown happens when the electric field gets sufficiently able to pull electrons from the atoms of the material, ionizing them. The delivered electrons are quickened by the field and strike different iotas, making all the free electrons. The particles in a chain response, flooding the material with charged particles. This happens at a trademark electric field quality in every material, estimated in volts per centimetre, is its dielectric strength.

Q.3. Does current controls a diode?

No, A diode is neither a current-controlled nor a voltage-controlled device. The diode only conducts if positive and negative voltages are correct.

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