diode

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Diode

A diode is an electronic device through which electrons can flow in only one direction. Because of its ability to control current flow, a diode is commonly used as a rectifier, a device that transforms alternating current into direct current.

In general, two types of diodes exist. Until the invention of solid-state devices such as the transistor, diodes were vacuum tubes containing two metal components. Later diodes are solid state devices consisting of adjacent regions of n-type and p-type (negatively-doped and positively-doped) semiconductor.

The working element in a vacuum tube diode is a metal wire or cylinder known as the cathode. Surrounding the cathode or placed at some distance from it is a metal plate. The cathode and plate are sealed inside a glass tube from which all air is removed. The cathode is also attached to a heater, which when turned on, causes the cathode to glow. As the cathode glows, it emits electrons.

If the metal plate is maintained at a positive potential difference compared to the cathode, electrons will flow from the cathode to the plate. If the plate is negative compared to the cathode, however, electrons are repelled and there is no electrical current from cathode to plate. Thus, the diode acts as a rectifier, allowing the flow of electrons in only one direction, from cathode to plate.

One use of such a device is to transform alternating current to direct current. Alternating current is current that flows first in one direction and then the other. But alternating current fed into a diode can move in one direction only, thereby converting the current to a one-way or direct current.

Newer diodes are made from n-type semiconductors and p-type semiconductors. N-type semiconductors contain small impurities that provide an excess of electrons (negative charge carriers, hence n-type) with the capability of moving through a system. P-type semiconductors contain small impurities that provide an excess of positively charged holesgaps in the atomic structure where electrons would normally be capable of moving through the semiconductor crystal (positive charge carriers, hence p-type).

A semiconductor diode is made by joining a sandwich of n-type semiconductor and p-type semiconductor through an external circuit containing a source of electrical current. The current is able to flow from the n-semiconductor to the p-semiconductor, but not in the other direction. In this sense, the n-type semiconductor corresponds to the cathode and the p-type semiconductor to the plate in the vacuum tube diode. The semiconductor diode has most of the same functions as the older vacuum diode, but it operates much more efficiently and takes up much less space than does a vacuum diode.

See also Electrical conductivity; Electric current.

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Diode

A diode is an electronic device that has two electrodes (conductors of electrical currents) arranged in such a way that electrons (subatomic particle having a negative charge) can flow in only one direction. Because of this ability to control the flow of electrons, a diode is commonly used as a rectifiera device that converts alternating current into direct current. (Alternating current is an electric current that flows first in one direction and then in the other. But alternating current fed into a diode can move in one direction only, thereby converting the current to a one-way flow known as a direct current.)

Types of diodes

In general, two types of diodes exist. Older diodes were vacuum tubes containing two metal components, while newer diodes are solid-state devices consisting of one n-type and one p-type semiconductor. (Solid-state devices are electronic devices that take advantage of the special conducting properties of solids. Semiconductors are substances that conduct an electric current but do so very poorly.)

Vacuum tube diode. The working element in a vacuum tube diode is a metal wire or cylinder known as the cathode. Surrounding the cathode or placed at some distance from it is a metal plate. The cathode and plate are sealed inside a glass tube from which all air is removed. The cathode is also attached to a heater which, when turned on, causes the cathode to glow. As the cathode glows, it emits electrons. The diode acts as a rectifier, allowing the flow of electrons in only one direction, from cathode to plate.

Semiconductors. Newer types of diodes are made from n-type semiconductors and p-type semiconductors. N-type semiconductors contain small impurities that provide an excess of electrons with the capability of moving through a system. P-type semiconductors contain small impurities that provide an excess of positively charged "holes" that are capable of moving through the system.

A semiconductor diode is made by joining an n-type semiconductor with a p-type semiconductor through an external circuit containing a source of electrical current. The current is able to flow from the n-semiconductor to the p-semiconductor, but not in the other direction. In this sense, the n-semiconductor corresponds to the cathode and the p-semiconductor to the plate in the vacuum tube diode. The semiconductor diode has most of the same functions as the older vacuum diode, but it operates much more efficiently and takes up much less space than does a vacuum diode.

[See also Cathode; Electrical conductivity; Electric current ]

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Diode

A diode is an electronic device that has two electrodes arranged in such a way that electrons can flow in only one direction. Because of this ability to control the flow of electrodes, a diode is commonly used as a rectifier, a device that connects alternating current into direct current. In general, two types of diodes exist. Older diodes were vacuum tubes containing two metal components, while newer diodes are solid state devices consisting of one n-type and one p-type semiconductor.

The working element in a vacuum tube diode is a metal wire or cylinder known as the cathode . Surrounding the cathode or placed at some distance from it is a metal plate. The cathode and plate are sealed inside a glass tube from which all air is removed. The cathode is also attached to a heater, which when turned on, causes the cathode to glow. As the cathode glows, it emits electrons.

If the metal plate is maintained at a positive potential difference compared to the cathode, electrons will flow from the cathode to the plate. If the plate is negative compared to the cathode, however, electrons are repelled and there is no electrical current from cathode to plate. Thus, the diode acts as a rectifier, allowing the flow of electrons in only one direction, from cathode to plate.

One use of such a device is to transform alternating current to direct current. Alternating current is current that flows first in one direction and then the other. But alternating current fed into a diode can move in one direction only, thereby converting the current to a one-way or direct current.

Newer types of diodes are made from n-type semi-conductors and p-type semiconductors. N-type semiconductors contain small impurities that provide an excess of electrons with the capability of moving through a system. P-type semiconductors contain small impurities that provide an excess of positively charged "holes" capable of moving through the system.

A semiconductor diode is made by joining an n-type semiconductor with a p-type semiconductor through an external circuit containing a source of electrical current. The current is able to flow from the n-semiconductor to the p-semiconductor, but not in the other direction. In this sense, the n-semiconductor corresponds to the cathode and the p-semiconductor to the plate in the vacuum tube diode. The semiconductor diode has most of the same functions as the older vacuum diode, but it operates much more efficiently and takes up much less space than does a vacuum diode.

See also Electrical conductivity; Electric current.

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diode Electronic component with two electrodes, used as a rectifier to convert alternating current (AC) to direct current (DC). Semiconductor diodes have largely replaced electron-tubes, and allow electric current to flow freely in only one direction; only a small current flows in the reverse direction. A Zener diode blocks current until a critical voltage is reached.

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di·ode / ˈdīˌōd/ • n. Electr. a semiconductor device with two terminals, typically allowing the flow of current in one direction only. ∎  a thermionic tube having two electrodes (an anode and a cathode).

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diode An electronic device, generally of semiconductor material, that has two terminals and is capable of allowing current flow in one direction only. The terminals are called the anode and cathode. The diode presents a very low (high) impedance when a forward bias (reverse bias) is applied.