A capacitor formerly known as a condenser, and prior to that
known as a permittor is a passive two-terminal electrical
component that stores electric
energy in an electric
field. The forms, styles, and materials of
practical capacitors vary widely, but all contain at least two electrical
conductors separated by an insulating layer. Capacitors are widely used as parts of electrical
circuits in many common electrical devices.
Video Source By- Learning Engineering
Electronic capacitors
are one of the most widely used forms of electronics components. However there
are many different types of capacitor including electrolytic, ceramic,
tantalum, plastic, sliver mica, and many more. Each capacitor type has its own
advantages and disadvantages can be used in different applications.
The choice of the
correct capacitor type is of great importance because it can have a major
impact on any circuit. The differences between the different types of capacitor
can mean that the circuit may not work correctly if the correct type of
capacitor is not used.
The ceramic capacitor is a type of capacitor
that is used in many applications from audio to RF. Values range from a few
picofarads to around 0.1 microfarads. Ceramic capacitor types are by far the
most commonly used type of capacitor being cheap and reliable and their loss
factor is particularly low although this is dependent on the exact dielectric
in use. In view of their constructional properties, these capacitors are widely
used both in leaded and surface mount formats.
Electrolytic capacitors are a type of
capacitor that is polarized. They are able to offer high capacitance values -
typically above 1μF, and are most widely used for low frequency applications -
power supplies, decoupling and audio coupling applications as they have a
frequency limit if around 100 kHz.
Like
electrolytic capacitors, tantalum capacitors are also polarised and offer a
very high capacitance level for their volume. However this type of capacitor is
very intolerant of being reverse biased, often exploding when placed under
stress. This type of capacitor must also not be subject to high ripple currents
or voltages above their working voltage. They are available in both leaded and
surface mount formats.
Silver mica capacitors are not as widely used
these days, but they still offer very high levels of stability, low loss and
accuracy where space is not an issue. They are primarily used for RF
applications and and they are limited to maximum values of 1000 pF or so.
Polystyrene capacitors are a relatively cheap
form of capacitor but offer a close tolerance capacitor where needed. They are
tubular in shape resulting from the fact that the plate / dielectric sandwich
is rolled together, but this adds inductance limiting their frequency response
to a few hundred kHz. They are generally only available as leaded electronics
components.
Polyester film capacitors are used where cost
is a consideration as they do not offer a high tolerance. Many polyester film
capacitors have a tolerance of 5% or 10%, which is adequate for many
applications. They are generally only available as leaded electronics
components.
This type of capacitor is a essentially a form
of polyester film capacitor where the polyester films themselves are metalized.
The advantage of using this process is that because their electrodes are thin,
the overall capacitor can be contained within a relatively small package. The metalized
polyester film capacitors are generally only available as leaded electronics
components.
As the
name implies, this capacitor type uses glass as the dielectric. Although
expensive, these capacitors offer very high levels or performance in terms of
extremely low loss, high RF current capability, no piezo-electric noise and
other features making them ideal for many performance RF applications.
Also known as a super capacitor or
ultra capacitor, as the name implies these capacitors have very large values of
capacitance, of up to several thousand Farads. They find uses for providing a
memory hold-up supply and also within automotive applications.