# Capacitor Voltage Rating

How to find the voltage rating of a capacitor after knowing the capacitance value.

Example, For a power supply, If the input voltage is 60V and output is 5V. The input capacitor(C1) value is 100uf and output capacitor value is 1000uf.

What is the voltage rating for both the capacitors and how to find them.

## 1 Answer

If the input voltage is 60 V, then a capacitor connected between the input and ground must be rated for at least 60 V, regardless of what capacitance it has.

If the output voltage is 5 V, then a capacitor connected between the output and ground must be rated for at least 5 V, regardless of what capacitance it has.

And of course it should actually be rated higher, in case the applied voltage varies, or there's a transient voltage applied. Some capacitor types will reduce in value as the applied voltage approaches the rating, perhaps by as much as 85%. Some capacitor types will have "recommended derating" information that might recommend using a capacitor rated for twice the actual applied voltage. Be sure to read the datasheets for any capacitors you're considering using to know whether they're appropriate for your circuit.