Diode

What is a Diode?

In my last article, i wrote a little on Transistor, its application and composition. Today, we will glance at a little of other semiconductor device in electronics.

A Diode is a semiconductor device that is made up of a P-N junction (positive-negative junction), sandwiched together. It is represented by the symbol shown below:

A diode only allows the flow of electric current in one direction i.e. when forward biased as shown in the diagram below. First, forward biasing a diode has to do with connecting or providing a signal source to the Anode (positive terminal) of the diode, while the cathode is then connected to the negative potential or ground of that same arrangement known as circuit in electronics terminology. This signal source could be a varying voltage from a transducer such as a microphone, thermistor (temperature-voltage converting device), a signal generator or even a DC power source such as the one used below and so on.

When a diode is reverse biased, current will not flow because it has a very high resistance when reverse biased. In the forward biased mode, current (conventional current) flows from the anode (positive terminal) to cathode (negative terminal). While electrons will migrate from the cathode (negative terminal) to the anode (positive terminal) of the semiconductor diode.

When you look closely to a practical diode, as in the most commonly used once such as IN4001 etc, there is a white coated ring like mark at one corner of the diode. This mark denotes the position of the cathode (negative) terminal while the other end that has uniform color with the rest part of the device is the anode (positive) terminal.

Applications of a Diode

A diode has vital and divers application in electronics circuit or in the field of science and technology in large. Among a few are in Logic circuits- where the presence and absence of a signal or voltage is denoted or represented as a 1 or 0. Diodes are used as OR Gates and other combination to form a complex unit. In Power Supply Units- Diodes are used in power supply circuits as rectifiers- It converts alternating signal (ac voltage) to direct current voltage (DC Voltage). Since it is said that current only flows in one direction, when the alternating signal is fed to it positive terminal known as the anode, current is allowed to flow through thereby forming a positive waveform at the output point. In Radio communication circuitry- Diodes are use as detectors for radio receivers (Amplitude Modulation Detector) in decoding or retrieving the signal received from the transmission end. In other circuits it could be manipulated to serve as a detector for heat and so on. The applications is much that diodes are now been use in television screen in their other forms as Light Emitting Diode. Light Emitting Diode- a Light Emitting Diode is just another form of a semiconductor diode been made to emits light when it is forward biased. This has brought further research work into complex designs as liquid displays and L.E.D television screens.

Another form of a semiconductor diode is a Zener Diode. In my next article I shall discuss more on it.

Watch out for my next article. Look forward to seeing you.
This is an update of my previous discussion on Diode.

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