How to Choose Capacitance in Circuit Design

Capacitance is also the most basic element in circuit design, so how to choose a suitable capacitor in electronic design?

1. Let's first learn about capacitance. The symbol of capacitance is C. The potential of capacitance is Farah (F). Farah is a very large unit. The commonly used units are mF (millimeter method), mu F (micro method), nF (nanometer method).

Unit conversion: 1F = 1000 mF, 1mF = 1000 mF, 1uF = 1000 nF.

The parameters of capacitor are: nominal capacitance value, each capacitor will be marked with corresponding capacitance values such as 2200 UF, 10 UF, 1nF, 104 (0.1 UF), in addition to nominal capacitance value, there should be corresponding errors, such as 10%, 5%, 0.5%.

Classification of capacitors:

According to the material, there are mica capacitor, ceramic capacitor, electrolytic capacitor, tantalum capacitor, polystyrene capacitor and so on.

According to the use, there are load capacitors, bypass capacitors, coupling capacitors, filter capacitors, etc.

According to polarity, there are polar capacitors and non-polar capacitors.

When choosing capacitors, they are selected according to their uses, such as energy storage, filtering, bypass, de-couple, load, high frequency, low frequency, etc.

For example, a capacitor is usually connected between the input end of the integrated circuit power supply and the ground. This capacitor belongs to the bypass capacitor. Its function is to filter the high frequency clutter of the power supply and eliminate the influence of the clutter of the power input on the chip.

The choice of this type of capacitor is related to the ripple coefficient of power input and the interference level of working environment. If the input of power chip is the best choice, the gallbladder capacitor is the best choice. The power terminal of other chips usually chooses 0.1uF ceramic capacitor.