Silicon diodes are semiconductors that allow electric current to flow in one direction while limiting it in another. They are made by adding small amounts of other elements to pure silicon, creating a pn junction. The diode has a forward bias of 0.7 volts and can protect other devices in a circuit. Zener diodes can maintain a fixed voltage.
A silicon diode is a semiconductor that has positive and negative polarity and can allow electric current to flow in one direction while limiting it in another. The element silicon, in its pure form, acts as an electrical insulator. To enable it to conduct electricity, small amounts of other elements are added, in a process known as doping. These make the charged semiconductor material used to build silicon diodes, which are then often used in radios, computers, alternating current and direct current (AC/DC) power supplies, and as sensors for temperature and radiation, among other applications.
When a silicon diode is made, it has both a positive and a negative side and a connection between the two, known as a pn junction. The two differently charged sides are the result of adding different elements to the silicon. The positive side, known as the anode and made of p-type silicon, is doped with boron or gallium. Their atomic structure, combined with silicon, creates the positive charge. Adding phosphorus or arsenic creates the negative cathode, made of n-type silicon, in a similar way.
The voltage of the silicon diode has a forward bias of 0.7 volts. This means that 0.7 volts are required to power the diode. Once this amount of energy passes through it, it will conduct electric current across its pn junction. It will also stop most of the current from flowing in reverse. Each silicon diode has a maximum voltage that it can be applied in reverse before it breaks down. This tends to be at least 50 volts or more.
In one sense, the diode can be thought of as an electrical check valve because it passes excess energy forward, but generally does not pass a measurable amount in reverse. A very small amount of current may, in fact, flow backwards through the diode, but it is so small that a circuit break from this amount would typically be rare.
Because a silicon diode generally only allows power to flow one way, it can be used to protect other devices in a circuit, such as transistors, from receiving too much power and burning out. Additionally, specially configured silicon diodes, known as Zener diodes, can be used to maintain a fixed voltage. These are made to intentionally conduct electricity backwards when needed in order to maintain a precise amount.
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