Capacitors are used in virtually every area of electronics, and they perform a variety of different tasks. Some capacitors are used for coupling, others for decoupling, while others may be used in filters, and some may be used for power supply smoothing. Again some capacitors will be used in low frequency circuits, and others in high frequency circuits.

There are many different types of capacitor, ranging from ceramic capacitors, to electrolytic capacitors, and silver mica capacitors to various forms of plastic (e.g. polyester) capacitors. Each capacitor type has its own advantages and disadvantages and therefore the uses of the capacitor can be different. Some are better for high frequency uses, whereas others can be used for low frequency applications. Indeed it is necessary to have the right capacitor for the right use of the circuit is to work properly.

Choosing the right capacitor use for the right capacitor is all part of the design process for a circuit. Using the wrong type of capacitor can easily mean that a circuit will not work.

Capacitors can be used in a variety of different ways in electronics circuits. Although their mode of operation remains exactly the same, they can be used to provide a variety of different circuit functions:

  • Coupling capacitor: to allow AC signals to pass from one section of a circuit to another while blocking any DC components.
  • Decoupling capacitor: to remove any AC signals that may be on a DC bias point or power rail.
  • Smoothing capacitor: This is effectively the same as a decoupling capacitor, but the term is normally used in conjunction with a power supply.
  • Timing element: In this application a capacitor can be used with a resistor or inductor in a resonant or time dependent circuit. In this function the capacitor may appear in a filter, oscillator tuned circuit, or in a timing element for a circuit such as an astable, the time it takes to charge and discharge determining the operation of the circuit
  • Temporary storage, etc. There are many other ways in which capacitors can be used.

In addition to the function within a circuit, there is also the frequency of operation that is of importance. Some capacitors operate better at low frequencies, whereas others are better at high or radio frequencies.