start in the fascinating and wonderful world of electronics by learning the very primary basics - modern capacitors




What are modern capacitors all about?

Over the last 100 years (I am taking some licence here because some sort of capacitors did exist back in 1900) there have been many remarkable changes in capacitor construction.

Types which were in vogue say 25 years ago are no longer satisfactory for the purpose required. One such type would be the silver-mica which was all the rage for frequency determining components in radio. Today I wouldn't consider it for a second because modern ceramic types are much, much more stable with well defined temperature coefficients and tolerances. Similarly the modern polystyrene types are vastly improved.

Here is a listing of some of the more common types and their properties.

Air variables

Quality air variables are rarely used today principally because of the costs involved. New air variables are almost prohibitively expensive for amateur radio or electronic hobby use. There is a large market of surplus or second hand types but even still they are relatively expensive and usually require a further expensive reduction drive and dial mechanism.

These today have largely been superseded by voltage variable diodes, frequency synthesisers and digital read outs.

Trimmer air variables have been replaced by more economical and miniature ceramic or plastic film types with a variety of ranges.

Miniature tuning capacitors

Ceramic capacitors

Ceramic capacitors are typically chosen for lower capacitance applications, where the operating frequency may be very high. Ceramics offer lower ESR than say tantalums. Also, ceramics offer an advantage in that they are less sensitive to transient voltages, and are not sensitive to polarity.

Blue chip monolithic capacitors

High voltage ceramic capacitors

Metallised polypropylene crossover capacitors

Non-polarised crossover capacitors

Tag Tantalum capacitors

Tantalums are generally chosen for applications where the operating frequency does not exceed 10 MHz, and where the required capacitance is very high.

Electrolytic capacitors

Super capacitors

Metallised Polyester or "Mylar" capacitors

MKT miniature polyester capacitors

MKT miniature polyester capacitors

Mains 250V AC capacitors

Power factor correction capacitors

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Updated 5th May, 2001