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Voltage rating is usually marked and is often identified by the symbol V. Most electrolytic capacitors clearly indicate their voltage rating. Polyester capacitors usually show the voltage rating but often omit the V symbol. Small ceramic capacitors often show no voltage rating. If the capacitance and voltage rating are both marked, a unit is also marked for at least one of the quantities so that the two cannot be confused.

Tolerance indicates how close a capacitor’s actual value is likely to be over or under its marked value. It is usually expressed as ±%.

Polarity sensitive capacitors, such as electrolytics, are usually marked with a + or - symbol adjacent to one lead to indicate polarity.

All real capacitors exhibit some change in value with varying temperature. Some ceramic types exhibit fairly linear changes and are useful as temperature compensating elements in AC circuits. The temperature coefficients of these types may be marked in letter codes or designated by a colour spot.

KP Polypropylene film/foil
KS Polystyrene film/foil
KT Polyester film/foil (polyethylene terephthalate PETP)
MK Metallised plastic film (general)
MKP Metallised polypropylene
MKT Metallised polyester (polyethylene terephthalate PETP)
MKT-P Metallised polyester/paper
MKY Metallised low-loss polypropylene
MKL (MKU) Metallised lacquer (cellulose acetate)

These offer low cost and high capacitance in a small physical size. Normally there are two types, the ‘High Stability Temperature Compensating’ type and the ‘Bypass and Coupling’ type. The former is for use in resonant circuit and filter applications, with a value largely independent of voltage and frequency. The latter is for use in less critical applications, as they are less stable and have non-linear temperature characteristics and are somewhat voltage dependent.

This type offer good stability, a large range of values at low cost and are the most widely used capacitor for general applications.

These offer tight tolerance and are highly stable, making them suitable for very stable tuned circuits and oscillators. Polystyrene is now an obsolete material and is being replaced by polypropylene capacitors in more and more applications. There is still a supply of polystyrene available on the market, but unfortunately the prices are likely to rise over the coming months and years. We at Maplin have, however, managed to secure a supply of polystyrene capacitors for at least the next 5 years and will endeavour to keep the prices stable for as long as possible.

This type have a very low dielectric loss and are particularly suitable in audio circuits and sample-and-hold circuits. They are also an ideal alternative to polystyrene capacitors.

Ideal for use in filtering and smoothing applications in power supplies. Also used for coupling and bypassing in audio circuits and as a timing element in non-critical circuits. They have a high reliability and low leakage. Since all electrolytic capacitors have a wide tolerance, one of the capacitors in our range will suffice in most cases where an electrolytic is specified. Choose the nearest value to the one specified and the nearest voltage equal to or above the one specified, e.g.: 50µF at 50V specified, nearest value 47µF and 100V is the nearest voltage above. Thus a 47µF at 100V will perform the same job as a 50µF at 50V in almost all applications, provided its physical size is not too large.

These are an ideal alternative to electrolytic capacitors, as they offer a smaller size and lower leakage.

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