On the Effects of Filter Capacitor Decoupling Capacitor and Bypass Capacitor(III)

Matters needing attention in the selection and use of capacitors:

1. In general, when the low frequency coupling or bypass is low and the electrical characteristics are low, paper and polyester capacitors can be selected; in high frequency and high voltage circuits, mica capacitors or ceramic capacitors should be used; in power source filtering and decoupling circuits, Electrolytic capacitors can be selected.

2, in the oscillation circuit, delay circuit, tone circuit, the capacitor capacity should be consistent with the calculated value. In all kinds of filter and network (frequency selection network, capacitor capacity requirement is accurate; in decoupling circuit, low-frequency coupling circuit, the same two-stage accuracy requirements are not too strict.

3. The rated voltage of the capacitor should be higher than that of the actual working voltage, and there should be enough room for it. Generally, the capacitor with a voltage value of more than twice the actual working voltage should be selected.

4. Choose the capacitor with high insulation resistance and low loss, and pay attention to the environment.

The typical decoupling capacitance in digital circuits is 0.1 μ F. The typical value of the distributed inductance of this capacitor is 5μH. . 1μF, 10μF capacitors, parallel resonant frequency above 20MHz, remove high-frequency noise better. A charge / discharge capacitor or a storage capacitor is added to every 10 or so integrated circuits, which can be selected around 10 μ F. It is better not to use electrolytic capacitors. The electrolytic capacitor is rolled up by two layers of film. This rolled structure shows inductance at high frequencies. Use tantalum or polycarbonate capacitors. The choice of decoupling capacitors is not critical and can be taken as C=1/F, that is, 0.1μF for 10MHz and 0.01μF for 100MHz.