How to select capacitor types according to frequency in filter circuit(II)

The following rules can be calculated from the upper formula:

1. when the working frequency is certain, the capacity C of the capacitor is inversely proportional to the equivalent series resistance ESR. The higher the ESR, the lower the product's capacity C will be. In turn, the lower the ESR of the capacitor, the higher the working frequency of the product will be applicable. This is that the capacitor manufacturer desperately seeks to produce a lower ESR capacitor. One of the fundamental reasons.

2. when the capacity of a capacitor at a working frequency must be required, the maximum ESR value allowed by the capacitor can be calculated on the basis of the above formula.

3. as long as we know the ESR value and capacity of a capacitor, we can calculate the appropriate maximum working frequency F of the capacitor according to the formula above.

The above three rules are very important for the circuit designers, especially in selection. Generally, the capacity attenuation of the capacitor at the appropriate working frequency is not greater than that of 20%.. The filtering effect begins to become worse and the amplitude of the clutter increases. At the same time, the reliability of the electric container will begin to decline. Filtering after the loss is also reduced. The waveform also begins to deviate from the design value.

Different types of capacitors have a very large difference in the equivalent series resistance due to their different structures. It is not only a large difference in capacity, but a great difference in temperature characteristics. In fact, different types of capacitors are suitable for filter use at different frequency ranges. Beyond this range, the capacity of capacitors will change greatly and can not meet the use of the capacitors. If you know enough about the basic performance of different types of capacitors, you can also choose the type of capacitor directly according to the working frequency range. However, the capacitor should be chosen in addition to the experimental confirmation. Understand the related knowledge to the manufacturer of capacitor.

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