Mechanical variable capacitors generally use air or plastic foils as dielectric. For this reason these dielectric capacitors are very useful in tuning circuits. High voltage type tuning capacitors have large air-gaps or spaces between the plates with relatively large break down voltages in order of kilo volts. In this design, when the two sets of metal plates are fully meshed together, the capacitance value is generally at maximum value. When the axis is turned, the area of overlap between the stator plates and rotor plates will vary and the capacitance is changed. The overall capacitance value (C) for this type of capacitors is determined according to the position of the moving metal plates with respect to the fixed metal plates. This setup is placed between a set of stator metal plates. Mechanical variable capacitors consist of a set of semi-circular metal plates fixed on the axis of a rotor. Symbols of Variable and Trimmer capacitors. The capacitance of variable capacitors is very small which is usually in the order of few picofarads (generally less than 500pF).įigure 1. They are generally not available for the use of regular customer. They are non-polarised capacitors and are very small in size. These are fixed on PCB’s and are used for the calibration of the equipment. There is another type of variable capacitors called Trimmer Capacitor. These capacitors are usually called Tuning Capacitors. Such capacitors are generally used in resonant circuits (LC circuits) for tuning radios and impedance matching in antennas. Variable capacitors are those in which the capacitance can be changed either mechanically or electronically. Like resistors, capacitors are also available as fixed and variable types. Despite the use of different kinds of dielectrics in the construction of capacitors, the functionality of the capacitor doesn’t change: to store energy in the form of electric charge between the parallel plates. The last three are used in electrolytic capacitors. Some of the common dielectrics used in the construction of capacitors are: Most of the capacitors are named after the dielectric used in the construction. It is difficult to find an electronic circuit without a capacitor. Depending on the application, appropriate capacitor should be chosen.įixed capacitors are more common types of capacitors. Similarly, some capacitors have very low leakage current and others have very high leakage current. So they are generally used in power supply circuits. For example, the rated voltage of an electrolytic capacitor is larger when compared to a ceramic capacitor in the similar capacitance range. These factors determine how and in what applications a particular type of capacitor can be used. This resistance becomes a problem when the capacitor used at high frequencies.
#Full range ceramic capacitor code chart series#
This is called leakage current.Įquivalent series resistance: The terminals of the capacitor have a small amount of resistance (usually less than 0.1Ω).
Leakage Current: A small amount of current will flow through dielectric as they are not the perfect insulators. It specifies the maximum voltage that can be applied across the capacitor. Working Voltage: It is an important characteristic of the capacitor. Size: Both the physical dimension and the value of the capacitance is important. Hence, when choosing a capacitor, following few of many factors must be considered. The characteristics and areas of applications may vary from one capacitor to other. Some of the common capacitor types are ceramic, electrolytic (which include Aluminium capacitors, Tantalum capacitors and Niobium capacitors), plastic film, paper and mica.Įach capacitor type has its own advantages and disadvantages. The key factor in distinguishing different types of capacitors is the Dielectric used in its construction. There are different types of capacitors available in the market.