Capacitors

Polystyrene

Polystyrene dielectric capacitors are available in a wide range of values, from 10pF to 10nF, and with voltage ratings from 50V to 630V. Polystyrene capacitors have good electrical characteristics and are ideal for timing and general purpose applications.

Polyester resistor

Polyester capacitors are available in values from 1nF to 10µF and with voltage ratings from 63V to 400V. Polyester capacitors are generally inferior when compared with polystyrene types and they are usually used for less critical applications, such as decoupling.

Polycarbonate

Polycarbonate capacitors generally operate over a wider temperature range than their polystyrene counterparts and are available in values ranging from 10nF to 10µF. Polycarbonate capacitors are often used in applications where a more rugged component is required - such as a supply filter.

Ceramic Disk

Ceramic disk capacitors are available in values from 2.2pF to 100nF and with voltage ratings which extend from 50V to over 1kV. Ceramic capacitors are not as electrically stable as other types and this makes them generally unsuitable for use in timing and other critical applications. Instead, this type of capacitor is normally used for decoupling where its low cost and small size make it ideal.

Electrolytic

Electrolytic capacitors are available in either radial or axial lead packages (this picture shows a radial lead capacitor designed for printed circuit mounting) and with values that range from 100nF to over 47,000µF. Electrolytic capacitors have a wide tolerance range (typically -10% to +50%) and this makes them generally unsuitable for timing and other critical applications. In addition, the electrolytic action requires a d.c. polarizing voltage which MUST be applied with correct polarity. Electrolytic capacitors are used extensively for decoupling, smoothing and as reservoir capacitors in power supplies.

Pre-set Solid-dielectric

This preset solid-dielectric capacitor has a capacitance which is variable from about 12pF to 65pF. This makes it ideal for "trimming" radio frequency tuned circuits where it provides precise tuning adjustment of resonant frequency.

Variable Solid-dielectric

Variable capacitors like this are used for tuning simple radio receivers where only a single L-C tuned circuit is used. This particular component provides a capacitance which varies from 20pF to 500pF.

Variable Air-spaced

This "dual-gang" capacitor comprises two variable capacitors adjustable by means of a single control shaft. Each section of the capacitor provides a value which varies from 12pF to 208pF. This type of component is used for simultaneously tuning the aerial [or antenna] and local oscillator tuned circuits in a superhet radio receiver.