What is a Diode: Resistance of Diode, Symbol, Types of Diode

What is a Diode?

diode is defined as an electronic device having two-terminal that conducts current only in one direction. it is operated with a specified voltage level. An ideal diode has zero resistance in one direction, and in the reverse direction, the resistance is infinite.


Resistance of diode

In the real-world, diodes cannot achieve zero or infinite resistance. Instead, a diode will have a resistance that allows flowing current in one direction, and in the reverse direction the resistance is very high. that prevent from current flow.

Semiconductor diode

These are the most common type of diode. These diodes begin conducting electricity only if we provided a certain threshold voltage in the forward direction. The diode is said to be “forward biased” when conducting the current flow forward direction. When connected the diode in the opposite direction within a circuit in the reverse direction.

The resistance is very high and the diode is said to be “reverse biased”. A diode will only block current in the reverse direction while the reverse voltage is within a specified range. Above this range, the reverse barrier breaks and the diode is damaged. That voltage is called reverse breakdown voltage. When the voltage of the circuit is greater

then the reverse breakdown voltage,the diode can conduct electricity in the reverse direction and the resistance is very high.

What is pn junction diode

It is the simplest form of the semiconductor diode. In ideal conditions, this PN junction behaves as a short circuit, when it is working on forward biased and as an open circuit when it works in the reverse biased.

The name diode is derived from the Latin word di–an odeIt means a device that has two electrodes.

Diode symbol

The diode symbol is given below. The arrowhead points in the direction of current flow in the forward biased condition. That means the anode is connected to the p-type and cathode is connected to the n-type. We can create a simple PN junction diode by doping pentavalent impurity also called donor impurity in one portion.

and trivalent impurity also called acceptor impurity in other portions of silicon or germanium crystal block. These doping make a PN junction at the middle point of the block. We can also form a PN junction, by joining a p-type and n-type semiconductor together through a special fabrication technique. The terminal that connected to the p-type is the anode. The terminal connected to the n-type side is called cathode.

Working Principle of Diode

A diode’s working principle depends upon the interaction of N-type and P-type semiconductors materials. An N-type semiconductor has a large number of free electrons and a very few numbers of holes. In other words, we can say that the concentration of free electrons in N-type is high, and the numbers of holes are very low in an N-type semiconductor.

Working Principle of Diode

Free electrons in the N-type semiconductor are majority charge carriers, and holes in the N-type semiconductor are minority charge carriers. A P-type semiconductor has a high concentration of holes and having a few numbers of electrons.

Holes in the P-type semiconductor are majority charge carriers,and free electrons in the P-type semiconductor are minority charge carriers.

Types of Diode

The types of the diode are as following:

  1. Zener diode
  2. P-N junction diode
  3. Tunnel diode
  4. Varactor diode
  5. Schottky diode
  6. Photodiode
  7. PIN diode
  8. Laser diode
  9. Avalanche diode
  10. Light-emitting diode


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