Question

I'm using a 3.3V zenor diode as one of the components for a surge protector. I want to add a capacitor and a polarized capacitor in parallel with the zenor diode. What do you suggest I should use if the input voltage is 12Vdc?

Answer 1

Zener diode is basically a voltage regulator.

It doesn't allow much changes in current though there is increase in voltage. The role of capacitors is to reduce the ripples and so that a constant dc voltage will be obtained.

Now non polarized capacitors can be used wherever you are planning to have a less voltage supply. Due to the dielectric being not chemical, it is unpolarized. So it only offers less capacitance. If you add this non polarized capacitor in parallel with a high voltage supply, they won't get charged resulting in voltage which is less than the required one.

While the polarized capacitors offer high capacitance due to the dielectric. So they can store the required energy and then discharge it at the set time using a resistor. (called as time constant) but we have to be careful while using these capacitors. Connecting them in wrong direction will damage the capacitor itself and the whole circuit too.

Coming to your case, 12volts is not a high voltage. You can use both unpolarized and polarized capacitors.

But as there is a chance of connecting polarized capacitors improperly, I would recommend you to use the unpolarized capacitor for your voltage regulator (zener diode) circuit.

To generalise, if you want to use high voltages use polarized capacitors. If not unpolarized capacitors are enough.

Hope this helps.

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