In this topic we will cover how the capacitor is connected in the circuits and how it affects the capacitance of the whole circuit and will also see the different types of Capacitors.

The capacitance of the capacitor depends on the permittivity , area of the plates and the distance between the plates .

The formula for the same is given as:

C = E*A/d

Taking Permittivity as constant as the area of the plates increases the capacitance also increases whereas as the distance between the plate increases the capacitance decreases .

Now lets Understand the concept of Capacitor when connected in series and parallel

    Capacitor in Series :

When capacitors are connected in series, the total capacitance is less than any one of the series capacitors’ individual capacitances. If two or more capacitors are connected in series, the overall effect is that of a single (equivalent) capacitor having the sum total of the plate spacings of the individual capacitors. As we’ve just seen, an increase in plate spacing, with all other factors unchanged, results in decreased capacitance.

Thus, the total capacitance is less than any one of the individual capacitors’ capacitance. The formula for calculating the series total capacitance is the same form as for calculating parallel resistances.

Series capacitance = 1/Ct = 1/C1+1/C2+1/C3

Where Ct is total capacitance.

Therefore, Ct = 1/(1/c1+1/c2+1/c3)

    Capacitor in parallel :

When capacitors are connected in parallel, the total capacitance is the sum of the individual capacitors’ capacitances. If two or more capacitors are connected in parallel, the overall effect is that of a single equivalent capacitor having the sum total of the plate areas of the individual capacitors. As we’ve just seen, an increase in plate area, with all other factors unchanged, results in increased capacitance.

Thus, the total capacitance is more than any one of the individual capacitors’ capacitances. The formula for calculating the parallel total capacitance is the same form as for calculating series resistances:

Parallel capacitance is Ct = c1+c2+c3
Where ct is the total capacitance

Types of Capacitor :

    Ceramic capacitor: 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 capacitor: Electrolytic capacitors are a type of capacitor that is polarised. 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

    Tantalum capacitor: 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 Capacitor: 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 Film Capacitor: 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 Capacitor: 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.

    Metallised Polyester Film Capacitor: This type of capacitor is a essentially a form of polyester film capacitor where the polyester films themselves are metallised. 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 metallised polyester film capacitors are generally only available as leaded electronics components.

    Poly carbonate capacitor: The poly carbonate capacitors has been used in applications where reliability and performance are critical. The poly carbonate film is very stable and enables high tolerance capacitors to be made which will hold their capacitance value over time. In addition they have a low dissipation factor, and they remain stable over a wide temperature range, many being specified from -55°C to +125°C. However the manufacture of poly carbonate dielectric has ceased and their production is now very limited.

    Polypropylene Capacitor: The polypropylene capacitor is sometimes used when a higher tolerance type of capacitor is necessary than polyester capacitors offer. As the name implies, this capacitor uses a polypropylene film for the dielectric. One of the advantages of the capacitor is that there is very little change of capacitance with time and voltage applied. This type of capacitor is also used for low frequencies, with 100 kHz or so being the upper limit. They are generally only available as leaded electronics components.

    Glass capacitors: 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.

Supercap: 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.