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Design & Technology


There are many different types of electrical and electronic components, including resistors, capacitors and diodes. Each of these has a specific use in a circuit.


Electronic components can be divided into two groups: discrete electronic components and integrated circuits (ICs).

Discrete electronic components

A selection of electrical circuit board components

Discrete (meaning separate) electronic components can be selected individually and put together to make a circuit. Examples of discrete components include resistorsresistor: An electrical component that restricts the flow of electrical current. Fixed-value resistors do not change their resistance, but with variable resistors it is possible to vary the resistance., capacitors [capacitor: Circuit component which stores and discharges electrical current. They are made from two parallel metal plates separated by an insulator (called a dielectric). ], diodes and transistors [transistor: Components which do not conduct electricity unless they are turned on by a (different) electrical current. This means they can be used as switches, amplifiers and in other ways. ].

Discrete components can also be used as components in circuits that include an integrated circuit. For example, a 555 astable [astable: An astable circuit gives a pulsed digital output. For example, it could be used to make an LED flash. ] integrated circuit requires two discrete resistors and a discrete capacitor to make it work.

Integrated circuits

These are miniature circuits etched onto a piece of silicon, often called a chip. These chips are fitted inside a protective plastic package and are manufactured in large quantities.

A dual-in-line surface mount package integrated circuit resting on a finger-tip

The circuits inside the package are arranged in different configurations depending upon the type of chip and its function. The most common type of configuration is called the dual-in-line or DIL package, which has two rows of connecting 'legs', one on each side.

You don't need to understand how the circuit inside a silicon chip works. It's best to think of ICs simply in terms of their function: eg as timers, counters, logic gateslogic gate: Digital electronic devices that allow an electronic system to make a decision based on a number of inputs. or operational amplifiers [operational amplifier: A device which takes a relatively weak signal as an input and produces a much stronger signal as an output. ] (op-amps).

Input output process block

Normally they are one of the process blocks in an electronic system, as in the image here:

When using ICs you need to know:

  • which pins have to be connected
  • the function of each pin
  • how the IC is connected to the power supply

A circuit diagram that includes one or more ICs should show the pin numbers and how the pins are connected to the rest of the circuit.

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