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Capacitors from left: Ceramic Disc, Polyester Layer, Polyester Film, Axial Electrolytic

Electrolytic Capacitors:

Electrolytic capacitors are polarity sensitive and must be connected correctly. The negative lead is normally indicated by arrows on the body pointing towards it. In the case of radial electrolytics (where both leads are at the same end of the case) the positive lead should be the longer one. The capacitance is normally marked on the body in Microfarads (uF), along with the working voltage, which must not be exceeded. For power supply decoupling this working voltage should be at least twice the peak voltage to allow a good safety margin.

Note that non-polarised electrolytic capacitors are also available for special applications.

Tantalum Bead:

These are also polarity sensitive. The positive lead is often marked by a + sign adjacent to it. Values are normally marked on the side.

Other Capacitor Types:

Other types of capacitors available include: ceramic, polystyrene, polyester, polypropylene and mylar. None of these types are polarity sensitive, and can be connected in either orientation. Some types have the value marked on the case, others (including ceramic) use a 3 digit code. This works in the same way as resistor coding but using numbers instead of colours. The first 2 numbers give the value and the last number is the multiplier. These give the value in Picofarads (pF), e.g. code 103 = 1 0 000pF (=0.01uF - see Capacitance Conversion Table). The tolerance and material may also be marked using codes, see Capacitor Markings for more details.

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