09-03-2017, 07:26 PM
At DC, which is its normal operating environment, no current can pass.
Current will only flow if there is AC present across the capacitor (with or without the presence of a DC voltage).
Capacitive reactance (think of this as AC resistance if you like) decreases with increasing frequency so current through the capacitor increases with frequency. This is why you often find capacitors such as yours in parallel with electrolytic decoupling capacitors which perform well at low frequencies but are not so good as the frequency rises. This ensures that the decoupling action is maintained at both low and high frequencies.
Under normal conditions, the AC voltage across the capacitors will be zero or very close to it - that is, after all, why these components are fitted in the first place - so the current will be equally low. That is very much a simplification - electrolytic capacitors, for example, can overheat and even explode if the internal series resistance rises too high, which is why you find that main smoothing capacitors, for example, will have maximum ripple currents specified in the data but it won't be a problem with a 33n foil capacitor!
Current will only flow if there is AC present across the capacitor (with or without the presence of a DC voltage).
Capacitive reactance (think of this as AC resistance if you like) decreases with increasing frequency so current through the capacitor increases with frequency. This is why you often find capacitors such as yours in parallel with electrolytic decoupling capacitors which perform well at low frequencies but are not so good as the frequency rises. This ensures that the decoupling action is maintained at both low and high frequencies.
Under normal conditions, the AC voltage across the capacitors will be zero or very close to it - that is, after all, why these components are fitted in the first place - so the current will be equally low. That is very much a simplification - electrolytic capacitors, for example, can overheat and even explode if the internal series resistance rises too high, which is why you find that main smoothing capacitors, for example, will have maximum ripple currents specified in the data but it won't be a problem with a 33n foil capacitor!
