Search me on Linktree! Link in my bio!
This is a 5V Voltage Regulator that converts 13Vpk-pk AC to 5V DC. This circuit uses an active op-amp to keep the voltage very close to the zener voltage. The BJT is only turned on when the input voltage is positive. The other remaining passive components, like the inductor and the capacitor, make sure that both current and voltage are as smooth as possible.