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Capacitor basic knowledge and application

The main parameters of the capacitor: capacity and allowable error. Rated operating voltage. Energy loss. Frequency characteristics. Temperature range.

The main characteristics of the capacitor: through the AC resistance DC. The smaller the capacity, the worse the low-frequency response is, the better the high-frequency response is, and the larger the capacity is.

The main application of capacitors: filtering. Coupling. Bypass. Timing. Resonance. Decoupling. Compensation. Dividing. Derivative.

Classification of capacitors:

1. According to the installation method: patch and plug-in, the difference is: A. The chip capacitor can be attached to the PCB by the chip mounter, or it can be soldered on the PCB by hand soldering. B. The plug-in capacitor is either manually soldered. It is either first inserted on the circuit board and then fixed on the PCB by wave soldering. In the design point of view, if the space and function are satisfied, the chip components are preferentially selected to reduce the product cost.

2. According to the withstand voltage of the capacitor, 6.3V. 10V. 16V. 20V. 25V. 35V. 50V.100V.400V.630V.1KV.2KV and so on. In the design, if the circuit voltage exceeds the rated voltage of the capacitor, the capacitor will explode or burn out. Generally, it is designed according to 70% of the rated voltage of the capacitor. Of course, it cannot be too large. Too much will increase the product cost.

3. According to the type: ceramic capacitor (MLCC). Electrolytic capacitor. Tantalum capacitor. X capacitor. Y capacitor. CBB capacitor. Monolithic capacitor, etc., the first five are the most used in general electronic design, and MLCC capacitors It is the largest of these five kinds of capacitors, MLCC capacitors are divided into NPO.X7R.X5R.Y5V, etc., most of the factors are selected X7R, and NPO and monolithic capacitors are used in places with particularly high stability requirements such as clocks. Circuits, high-frequency resonant filter circuits, etc., tantalum capacitors are mostly used in applications where high stability and large capacity are required. In addition, electrolytic capacitors and tantalum capacitors must be distinguished by strict positive and negative poles. Burst and short circuit. CBB series capacitors are mainly used in high-voltage design circuits such as pulse, RC, buck, bypass, motor start, etc. X capacitors and Y capacitors are mostly used in the design of high-voltage circuits, which are safety capacitors, that is, capacitors will not fail. Damage to the human body, X capacitors are used to suppress differential mode interference, and Y capacitors are used to suppress common mode interference.

4. According to the size of the size: patch and plug-in, A. SMD package type: 0201 0402 0603 0805 1026 1210 1812 2010 3216. 3528. 6032. 7343, etc., if there is no special requirements in the design, choose this type of capacitor (MLCC capacitor), low cost and convenient production. B. The plug-in capacitors are also different according to the different sizes of the withstand voltage and capacity. Such capacitors are not recommended because they are not convenient to install. Of course, in the design of power supply filters and high-voltage circuit filter circuits, large capacity is required. Most of the high-voltage capacitors are plug-in type electrolytic capacitors.

6. According to the accuracy of the capacitance value: NPO is generally below 5%, Y7R ceramic capacitor K is 10% and M20%, tantalum capacitor is 10%-20%. Y5V and electrolytic capacitors are generally above 20%. Of course, the accuracy of small-capacitor capacitors will be lower.

7. Capacitance value identification: Generally, there is no indication on the MLCC component. It can only be marked by the package or measured by actual measurement, such as 102=1nF, 472=4.7nF, 100=10PF, 105=1uF, the first 2 digits are valid numbers. The next number is the number plus 0, the unit is pF. Of course, you can also use the bridge to measure its capacitance value, 1uF=1000nF=1000000pF


Post time: Mar-22-2019
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