The Basics of Diodes

The Basics of Diodes

Diodes are specialized electronic components that act as one-way switches, conducting current in only one direction and restricting current from flowing the other way.diodes They are used in a wide variety of circuits such as signal modulators, signal mixers, rectifiers and voltage regulators to help prevent circuit damage from overvoltage, as well as in DC power supplies to convert AC current into DC current.diodes

Every diode has two terminals -- connections on each end of the component called the anode and cathode.diodes The anode terminal has a positive (or negative) electrical charge, while the cathode terminal is negatively charged.diodes Since the terminals are polarized, it is important to note which ends they are connected to so that current will flow through the diode in the correct direction. A simple mnemonic to remember this is: ACID. The "arrow" on the diode symbol depicts the standard direction of current flow, from positive (+) to negative (-). Diodes can only be forward biased; they cannot be reverse-biased because the electrons inside them would quickly be stripped away.

The fundamental nature of a diode is determined by the chemical makeup of the semiconductor material from which it is made.diodes In most cases, the two sides of a diode are made from different semiconductor materials.diodes These are usually N-type and P-type materials that combine to form a P-N junction. This junction is where the narrowing space forms that allows current to flow through the diode. When a positive voltage is applied to the n-side of this junction, electrons from that side begin to move into empty spaces on the p-side and create a depletion region. The electrons and holes then diffuse across the junction, and the diode begins conducting current.

When a negative voltage is applied to the cathode of a diode, a hole moves from the n-side into the p-side of the semiconductor crystal.diodes This causes the hole to fill with an electron, creating a depletion region on the p-side of the semiconductor.diodes The positive voltage on the anode side of the diode forces electrons out of the p-side to fill the holes, and the diode stops conducting current in the opposite direction.

This process of current flow through a forward-biased diode can only take place at a certain temperature, which is determined by the chemical makeup of the semiconductor from which it is made.diodes As the temperature of the semiconductor increases, the current through a forward-biased diode decreases. This characteristic is exploited in devices such as Zener diodes for the generation of extremely short pulses of current. The reverse current that can flow through a reverse-biased diode depends on the amount of stored charge in the depletion region. For large values of this charge, the depletion region will expand rapidly and allow for a relatively high reverse current to pass through the diode. For small amounts of charge, however, the depletion region will remain relatively stable and prevent current from passing through the device.