Electronic – Why use capacitors


Why do you need to store the voltage for some time in a capacitor? I've always assumed circuits to work when you power it on and stop when you power it off.

Why can't the whole circuit be drawn capacitor free? If it's meant for storage why not just use a flip-flop?

Best Answer

If all you wanted to build was digital circuitry, and your voltage sources really held constant voltage no matter how much current was drawn from them, and nothing produced electrical noise, you wouldn't need capacitors.

But voltage sources sag when you draw current from them. Motor brushes (and lots of other components) produce horrendous voltage spikes that you want to filter out of your digital circuitry. Some people also deal with analog circuitry, where voltage and current signals vary continuously across a wide range. For that kind of time-varying circuitry, capacitors are needed.