Why do I need a capacitor between power and ground?

Capacitors between power and ground is used to suppress spikes. These spikes can damage the board, or at least, the sensitive components. The larger the value of the capacitor, the better the protection. Hope this helps. What is your application/circuit? If it's on a long power line, it could be to just make sure that all AC signals are bypassed.

What are the characteristics of a capacitor?

) Parasitic capacitors to ground from each node of the capacitor. ) The density of the capacitor in Farads/area. ) The absolute and relative accuracies of the capacitor. ) The Cmax/Cmin ratio which is the largest value of capacitance to the smallest when the capacitor is used as a variable capacitor (varactor).

Why is a ceramic capacitor better than an electrlytic capacitor?

The electrlytic capacitor has high current capacity so that it can carry large spike current when there is any spike in the power supply line. But the frequency responce of the capacitor is less which allows the spike to be present to some extent. The ceramic capacitor is good at frequency response, so it blocks the spike at the output.

What ohm is a good ground resistance?

The telecommunications industry has often used 5 ohms or less as their value for grounding and bonding while electric utilities construct their ground systems so that the resistance at a large station will be no more than a few tenths of one ohm. In general, the lower the ground resistance, the safer the system is considered to be.

Why are capacitors paralleled with smaller values?

This is why in decoupling applications we often see larger value capacitors paralleled with smaller values. The smaller value capacitor will typically have lower ESL and continue to behave like a capacitor at higher frequencies. The parallel combination of capacitors covers a wider frequency range than either one of the combinations. Figure 2.

What is the relative accuracy of a capacitor?

Capacitor relative accuracy is proportional to the area of the capacitors and inversely proportional to the difference in values between the two capacitors. For example, The following scheme will tend to keep the relative accuracy constant as a function of the ratio of capacitors.