Transistors Integrated circuits Capacitors Light emitting diodes

In electronics, miniature components are often used. In this section you will learn their symbols, and what each component does.

Transistors
Transistors are tiny semiconductor devices that are used to switch or amplify currents and voltages. There are many different types designed to perform specialised tasks. Transistors allowed radios to be made portable as they replaced cumbersome valves. Portable radios are sometimes called "transistors" or "trannies". The transistor was invented in 1947, and the three inventors, William Shockley, John Bardeen and Walter Brattain, won the Nobel Prize for Physics in 1956.

Transistors can operate as switches or amplifiers, making them very useful components in electronics. Transistors are polarised and must be connected the right way round. Two types are NPN (negative - positive - negative) and PNP (positive - negative - positive).

Integrated circuits
Integrated circuits (ICs) can have many components for a radio on a tiny silicon "chip", which enables electronic equipment to be extremely small. An example is the identification chip that can be placed under your pet's skin in case it gets lost. Simple ICs have three pins, ICs in your computer have many more pins. Modern computers and other devices can have hundreds of intergrated circuits combined into one chip. A CPU (Central Processor Unit) is an IC that can perform hundreds of tasks per second or faster and may contain 20 million or more transistors.

	Basically, capacitors store electrical energy, then release it in one hit. This is the symbol for a polarised capacitor: Note how this differs from the symbol for a cell - both lines are the same length.
The unit for capacitance is the Farad, named after the Englishman, Michael Faraday. In the circuits you are likely to use, capacitance is measured in microfarads (µF), or a unit one thousand times smaller, the picofarad (pF).

In miniature circuits, light globes are too big. The small coloured light on your stereo, computer or video camera is a light emitting diode (or LED). Light emitting diodes are used in the flashing red lights that cyclists have on their bikes. They don't use much power and, by using capacitors in the electronic circuitry, the lights flash as well.

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