Diodes were the first Semiconductor devices invented and developed in the mid 18th-19th century. It has replaced the vacuum diode which produces excess heat and also occupies much space. Since the invention of diode, the electronic industry has boost significantly and pave way for transistors, LASER diodes and other semiconductor components.
How diode was invented.
The discovery of crystals rectifying abilities in year 1874 was attributed to Ferdinand Braun a German physicist. The first semiconductor known as whisker diode were made from a mineral crystal of Galena. Today most diodes are manufactured from silicon, other semiconductors like germanium were little used. Diodes was invented to replace vaccum tubes because of their inefficiency and the space they occupies, today diodes are not up to size of a finger nail. Vaccum tubes have anodes and cathode both evacuated in a glass envelope the cathode is heated by an element to produce electrons, it is then connected appropriately in circuits to rectify and block current. A great difference between a diode and a vaccum tube is that it doesn't need to be heated and don't use up any voltage since it is a passive component.
What is a diode?
Without beating about the bush, diode is an electronic component that allows current to flow in one direction. A diode is made from semiconductors like silicon and germanium now of little use. It is made from junction of a P-type and an N-type semiconductor. Naturally a Semiconductor can't conduct current in it pure state , hence they are insulators at this state. When a material which has much electron is mixed (doping) with silicon or germanium it produces an N-type, also when a substances with much holes or proton is forced into silicon or germanium it produces a P-type.
A P-type and N-type semiconductors has only holes and electrons respectively, when both are marged together to form a junction which is called a P-N junction diode. As shown above when a direct current is applied to it with negative terminal connected to the N-type and positive polarity to the P-type current flows freely, but when the polarity are reversed their is no current flow, hence it can be use for rectification and filtrating of unwanted signals.
Types of diodes.
There are many types of diodes, but one common properties is that they allow current to flow in one direction. Some are use for current regulation, lightning, burning and photomentry.
- Light emitting diodes
- Normal diode
- Zener diode
- LASER diode
- Photo diode
- BARRIT diode
- Avalanche diode
- Tunnel diode
- GUNN diode
- Varicap or veractor diode.
- Step recovery diode
- PIN diode
- Constant current diodes
- Shockley diodes.
1. Light emitting diode.
This type of diodes emits light when connected to an electric current in the forward bias. It is the combination of a P-type semiconductor and a N-type semiconductor, when current is applied to it, electrons and hole combines produce light. The color of light they emit depends on the type of semiconductor used.
2. Normal or rectifier diodes.
3. LASER diodes.
These types of diodes conducts electricity only in the reverse bias when current greater than it knee down voltage is connected to it. It was invented by Dr. Clarence Melvin zener from southern Illinois. Zener diodes are use for led indicators, voltage regulation and voltage reference.
It is a semiconductor junction device that produce a coherent beam of light when connected in forward bias to a power source.
LASER stands for light amplification by stimulated emission of radiation.They can be made to produce straight beam of red, blue and green light. LASERs are use for burning, optical communication, gun sight and measuring aquatic animals underwater.
4. Zener diodes.
5. Photodiodes.
It converts light or photons into voltage, current or signal. It semiconductor is intentionally made to get exposed light. Photodiodes are use in solar panels because they convert light to current and are use in remote control system and photo communication.
6. Tunnel diodes.
The tunnel diode is a highly conductive, heavily doped PN-junction diode in which the current induces because of the tunnelling.
7. BARRIT diodes.
It has a full meaning of barrier injection transit time diode. BARRITs generates microwaves when connected to a power source. It is use in telecommunication and micro wave ovens.
8. Gunn diodes.
GUNN diode is a PN junction diode, this sort of diode is a semiconductor device that has two terminals. Generally, it is use for producing micro wave signals.
9. Varicap/veractor diodes.
They are diodes whose capacitance or reactance depends on the voltage applied to them. Veractor are called variable reactor diodes while varicap means variable capacitance diodes. They are highly use in electronics because they provide a variable capacitance in a circuit by the controlled voltage, thus they are highly employed in radio frequency and radio circuits design. Their applications includes radio frequency filter as a demolator and tunning into frequencies, frequency, phase modulator and voltage controlled oscillators.
10. PIN diodes.
It converts light and optical charge into electrical signals, thus they are use for detecting optical charge and they are widely employed in optics measuring instruments. They are also use for switching RF signals.
11. Shockley diodes.
The diode is a semiconductor device has four layers labelled as PNPN. It also called as PNPN diode, it can stay on and off. It has two operating state, conductive and non-conductive, in the conductive state it conducts with much voltage while the non-conducting conducts with little voltage.
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Basic Electronics