What is Capacitors
Capacitors
are two-terminal elements used for filtering, energy storage, voltage spike
suppression, and lots of alternative applications. In their simplest form, they
consist of two parallel plates separated by an insulating material called a
dielectric. Capacitors store electrical charge.
Capacitors Types
There are several different
types of capacitors
Aluminium Electrolytic Capacitors
Ceramic Capacitors
Tantalum Capacitors
Film Capacitors
Polymer Capacitors
I. Aluminium Electrolytic Capacitors
Characteristic: aluminium Electrolytic Capacitors ar polarized, so
that they can't be used with AC. They can achieve high capacitance value but
with large variations, typically 20%.
Applications: These are useful in applications which do not need
tight tolerances or AC polarization. They are most commonly used in power
supplies for decoupling purposes, i.e. to reduce voltage ripple reaching the
circuit. They are additionally used wide in DC/DC switch voltage converters.
II. Ceramic Capacitors
Characteristic: There are two main types of ceramic capacitors:
Multi-layer chip capacitors
(MLCCs) and ceramic disc capacitors. MLCCs are very widely used in electronic
devices and are popular because they have high stability and low losses. They
have lower Equivalent Series Resistance (ESR) and variation compared to
electrolytic or tantalum capacitors however are able to do lower capacitance
(only up to a couple of µF) . Because of high packing densities, MLCC
capacitors provide a size advantage and are great for printed circuit boards
(PCBs).
Applications: Since these are not polarized, they can be be used
with AC. They are wide used as a ‘general-purpose’ electrical device and used
for prime frequency interference, filtering, generator standardization and EMI
suppression. Both MLCCs and ceramic disc capacitors ar more divided into 2
application classes:
Class I ceramic capacitors are
accurate ( 5%) and temperature-compensated- they have very low change of
capacitance with temperature. NP0/C0G ar standard, and have a tolerance of
30ppm/K, but are available only up to the nanoFarad (nF) range. Because they
are very stable and accurate, they are used in frequency control applications
such as resonant circuits for radio applications.
III. Tantalum Capacitors
Characteristic: These are a subtype of electrolytic capacitors and
are highly polarized. Care needs to be taken as they are known to have
catastrophic failure modes which can be triggered by voltage spikes even
slightly more than rated voltage. They can achieve high capacitance value and
are very stable over time. They are smaller in size than aluminum electrolytic
capacitors of a similar capacitance however will handle lower most voltages.
Applications: because of their low leak current, stability, and
high capacity, they are common for sample and hold circuits which rely on low
leakage current to achieve long hold duration. They are additionally utilized
in power offer filtering because of their smaller size and long term stability.
IV. Film Capacitors
Film capacitors ar non-polarized
that makes them appropriate for AC signal use. They have low Equivalent Series
Resistance (ESR) and coefficient of self induction (ESL) and ar utilized in A/D
converters. They can handle high peak current and can thus be used as snubber
capacitors to “snub” inductive kickback voltage spikes in DC-DC converters
V. Mica Capacitors
Mica capacitors ar
non-polarized, have low losses, high stability, and have great high-frequency
properties. They are useful for radio frequency circuits. Mica capacitors will
price a couple of greenbacks per piece, so they are being replaced by ceramic
capacitors for low-power applications. However, they continue to be important
for prime power applications like RF transmitters because of their high
breakdown voltage.
VI. Polymer Capacitors
Polymer capacitors are polarized
similar to different electrolytic capacitors however have many benefits like
lower losses because of lower ESR and longer time period. For typical aluminium
electrolytic capacitors, there is a risk of electrolyte dry-out at lower
temperatures, but due to the use of solid polymer material as dielectric,
polymer capacitors have high reliability even at very low temperatures.
Polymer capacitors ar utilized
in place of electrolytic capacitors for prime quality motherboards and DC-DC
converters.
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