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Proper understanding of the definition of
capacitors.
Identify the relationship between a resistor
and a capacitor.
Calculate capacitance in series and parallel
circuit and in terms of same capacitance
value.
Classify capacitors according to materials and
usage.
Relate the topic to everyday living.
A capacitor is a device that stores
electrons. The basic capacitor is made up
of two conductors separated by an
insulator, or dielectric. Depending on how
the capacitor is built, the dielectric can be
made of paper, plastic, mica, ceramic,
glass, a vacuum or any other such non
conductive material.
Capacitor electron storing
ability (its capacitance) is measured
in Farads. 1 Farad is actually a huge
number of electrons (6, 280, 000,
000, 000, 000, 000 electrons to be
exact), so we usually rate capacitors
in microfarads (µF) and picofarads
(pF).
1 µF is equal to 0.000001 F
1 pF is equal to
0.000000000001 F
Capacitors comes in a
variety of sizes, shapes,
models, or if you so desire they
can be manufactured by your
specifications.
Capacitors also come in a variety
of materials, to name a few :
Aluminum foil, Polypropylene,
Polyester (Mylar), Polyesterene,
Polycarbonate, Kraft Paper, Mica,
Teflon, Epoxy, Oil-filled, Electrolyte,
Tantalum, and the list goes on. Latest
product (in reseach) is Nobium.
The value of a capacitor can
vary from a fraction of a picofarad to
more than a million µF (µ means
´micro´). Voltage levels can range
from a couple to a substantial couple
hundred thousand volts.
It
can store electric charge even
though the voltage source is already
disconnected.
It
can discharge electrical voltages.
An early classification is settled
for capacitors. These were
stablished and categorized into
four namely (a)non-polarized ,
(b)polarized, (c) variable, and (d)
trimmer.
Non-polar capacitor is a type of
capacitor that can be connected any
way in a circuit. In other words, there
is no positive or negative. Common
types of non-polar capacitors are
ceramic,mica and some electrolytic.
There are two types of nonpolarized capacitors. The plastic foil
that are non polarized by nature and
electrolytic non polarized capacitors
that are actually two capacitorsin
series (back to back) so that the
result is non polarized with half the
capacitance.
A capacitor stores electric charge. This
type must be connected the correct way
around. A capacitor stores electric
charge. A capacitor is used with a
resistor in a timing circuit. It can also be
used as a filter, to block DC signals but
pass AC signals.
Polarized capacitors are the
electrolytic type or tandalium type.
They have large leakage current if the
voltage is inverted. They are cheaper
than equivalent non-polarized
capacitors. They are sometimes
physically smaller that non-polarized
equivalents. They are meant for AC
signals respectively.
Electrolytic capacitors have a
polarity unlike other capacitors. This
is due to the fact that aluminum
oxide layer is held in place by the
electric field, and when reversebiased, it dissolves into the
electrolyte. This allowsa short circuit
between the electrolyte and the
aluminum.
Non-polarized capacitor has a big size with the
smaller capacitance, and is used both in DC or
AC circuits, low or high frequencies.
Polarized capacitor has a small size with the
large capacitance, and is used only in DC
circuits or circuits related to DC current.
Non-polarized capacitor has a very small leakage
current, high frequency response of up to
hundreds of GHz up to types.
Polarized capacitor has a large leakage current
low frequency response of only up to about
tens of kHz at aluminum or 1MHz at tantalium
caps.
In general, they
cannot replace each
other!!!
A variable capacitor is a
capacitor whose capacitance can be
varied. These are usually made up of
one or more moving plates and one or
more non moving plates separated by
the dielectric. By moving the plates, we
can vary the capacitance. A variable
capacitor is used in a radio tuner.
This type of variable
capacitor (trimmer) is operated
with a small screwdriver or
similar tool. It is designed to be
set when the circuit is made and
then left without further
adjustment.
FIXED / NORMAL /NON-POLARIZED
Ceramic capacitors – dip guard, monolithic (axial
leads), monolithic (radial leads), disc, surface
mount
Film capacitors – polyester (axial leads),
polyester (radial leads), polypropylene (axial
leads), polypropylene (radial leads),
polystyrene (axial leads)
POLARIZED CAPACITORS
Aluminum Electrolytic capacitors – axial leads,
radial leads, computer grade, snap mount, twist
lock, surface mount
Tantalum capacitors – solid tantalum (axial leads),
solid tantalum (radial leads), foil tantalum (axial
leads),foil tantalum (radial leads), dipped
tantalum, wet tantalum, surface mount
VARIABLE CAPACITORS
1.
Semiconductor diodes – rectifier, zener, LED
2.
Bipolar Junction Transistors (BJT) – PNP, NPN
3.
Integrated Circuit