How do diodes regulate current flow in circuits?

Diodes regulate current flow in circuits by allowing it to flow in one direction only.

A diode is a semiconductor device that acts as a one-way valve for electric current. It is made from a piece of semiconductor material with a 'p-n junction'. The 'p' side, known as the anode, has an excess of positive charge carriers (holes), while the 'n' side, known as the cathode, has an excess of negative charge carriers (electrons).

When a voltage is applied across the diode in the forward direction (positive to the anode, negative to the cathode), the positive holes in the anode are attracted to the negative terminal of the voltage source, and the negative electrons in the cathode are attracted to the positive terminal. This allows current to flow through the diode.

However, if the voltage is applied in the reverse direction (positive to the cathode, negative to the anode), the positive holes and negative electrons are both attracted towards the middle of the diode, creating a 'depletion region' where there are no charge carriers. This prevents current from flowing through the diode.

In this way, diodes can be used to regulate the direction of current flow in a circuit. They are often used in power supply circuits to convert alternating current (AC), which flows back and forth, into direct current (DC), which flows in one direction only. This process is known as rectification.

It's important to note that diodes are not perfect, and a small amount of current can sometimes leak through in the reverse direction. This is known as the 'reverse leakage current'. Also, diodes have a 'forward voltage drop' - a minimum voltage that must be applied in the forward direction before current will flow. This is typically around 0.7 volts for silicon diodes.