The Capacitance, also known as the Capacitance, refers to the charge storage at a given potential difference. The symbol is “C”. The SI unit is Farad. The commonly used capacitance units are millimetric (mF), micrometric (μF), nanometric (nF) and cuticle (pF). The specific conversion method is as follows:
1 farad (F) =1000 milieu (mF) =1000000 micromethod (μF)
1 micromethod (μF) = 1000 nano method (nF) = 1000000 skin method (pF).
Capacitors are mainly used in power filtering, signal filtering, bypass, signal coupling, resonance, compensation, energy storage, DC isolation and other circuits in the electronic field. In analog circuits, capacitors play more roles, in digital circuits, capacitors are mainly used as filters.
The types of capacitors can be divided into non-polar variable capacitors, non-polar fixed capacitors and polar capacitors in principle. In terms of materials, they can be divided into: CBB capacitance (PE), polyester capacitor, ceramics, mica capacitors, monolithic capacitors, electrolytic capacitors, tantalum capacitors, etc., among them, in the process of application, tantalum capacitors have to be very attention to the polarity, namely the positive and negative can’t reverse, otherwise once produce, tantalum capacitor is blow up directly, but also on fire, although compared with electrolytic capacitor performance better, but also more dangerous and expensive.
There are also many types of capacitor packages. For ceramic capacitor, there are 0201,0402,0603,0805,1206,1210,2012, etc. For tantalum capacitor, there are 3216,6032,7343, etc. There are more electrolytic capacitors.
Capacitance parameter, generally marked on the device surface, in addition to the patch of ceramic capacitor, the capacitor will not have a capacitance annotations, other basic will mark, mark is much capacitance aluminum electrolytic capacitor will directly, most of the other need conversion, the reading of the capacitance and resistance, such as tantalum capacitor surface with a 106, It means 1*10^6=1*1000000=10000nF=10uF.
In the selection of capacitor packaging, usually according to the application to choose, general capacitance will be large, because it is cheap, but due to space constraints and other reasons, it has to choose a small volume of packaging, in the selection of capacitance is usually look at the voltage value, capacitance, packaging, voltage value according to the circuit to determine, For example, the capacitor should be used as the input filter capacitor (filter clutter signal) of the power supply. If the power input is 12V, the capacitor should be 25V, and the voltage value should be at least 1 times higher than the voltage at both ends, so as to ensure that the capacitor is not easily damaged. The capacitance and packaging need to be selected and determined according to the following conditions. For example, the power pin of a chip is usually filtered with a capacitor of 0.1uF /0603/16V (0.1uF is the empirical value).