Electrical circuits have active circuits and passive circuits in electronics. There are diodes as the first active components. And resistors are the first passive components in electronic design circuits. However, they do have little diodes with such exponential behavior characteristics made from semiconductor materials. Let’s understand what semiconductor diodes are.
Definition
The specialized electronic component known as a diode is a one-way switch. It conducts current in one direction, while denying or restricting it completely in the opposite direction. A diode becomes reverse biased when it stops conducting and behaves like an insulator, while it becomes forward biased when conditions allow current to flow through it. A diode has two terminal connections: an anode and a cathode. Engineers use diodes in numerous applications, where they serve various purposes, including acting as switches, signal modulators, signal mixers, rectifiers, signal limiters, voltage regulators, oscillators, and signal demodulators.
Structure
Manufacturers create diodes using two semiconductor materials: an N-type material, which is rich in negative carriers or free electrons. And a P-type material, which is rich in positive carriers or holes. Joining these materials forms a junction, which gives the diode its alternate name: the PN Junction. Applying a voltage that causes the junction to allow electrons to flow from the anode to the cathode forward biases the diode. In contrast, a diode becomes reverse biased when, despite the applied potential, the junction prevents a steep rise in current, allowing only a very small and practically negligible current to flow across it. When forward biased the diode acts like a closed switch; when reverse biased it behaves like an open switch.
Functions
The characteristic current-voltage (I-V) profiles of a diode govern its operation. Connecting the positive (highest) potential to the P material and the negative to the N material in a circuit forward biases the diode. Conversely, connecting the highest potential to the N material and the lowest to the P material reverse biases the diode.
Types of Diodes
- General purpose diodes are electronic components providing two terminals which only allow current to flow from an anode (+) to a cathode in one direction.
- Light-emitting diodes (LEDs) forward biased are therefore p-n junction devices which emit light radiation through electroluminescence. They are used as indicators in say, aviation, automotive and some traffic lighting. They are also used in some torch and lamp bulbs.
- Photodiode is the two electrode, light sensitive junction created in semiconductor material where reverse current varies with illumination.
- The PIN diode is a three-layer semiconductor diode that consists of the intrinsic layer in between heavily doped P and N regions.
- In tunnel diodes, electron tunneling from the conduction band in the N-type material into the valence band in the P-type region creates an area of negative resistance due to the heavy doping of the P-N junctions.
The schematic symbol used for semiconductor diodes is typically an arrow with a short line across the tip. The cathode is the N-type material and is represented by the tip of the arrow. The anode is the P-type material and is indicated by the base of the arrow.
