Power diodes are used mainly in high-power applications. They are built with large P-N junctions in order to pass large amounts of current and dissipate large amounts of heat. Power diodes can also withstand high voltage diodes when operated in reverse bias. There are many different types of power diodes. Examples include high current diodes, high voltage diodes, PN power diodes, PIN power diodes, RF power diodes, switching power diodes, and rectifier power diodes. Basic power diodes consist of a diode built into a chip. Power diode arrays are composed of multiple, discrete, and usually unconnected devices on a single silicon chip. Pin count and number of embedded diodes varies by integrated circuit (IC) package type. Power diodes that are sold in Europe must comply with the Restriction of Hazardous Substances (RoHS) directive from the European Union (EU).
Performance specifications for power diodes include junction operating temperature, reverse recovery time, repetitive peak reverse voltage or maximum reverse voltage, peak forward surge current, reverse current, and forward voltage. Junction operating temperature is the range of temperatures over which power diodes are designed to operate. Reverse recovery time is the time taken for the reverse current to reach a specified level when the reverse voltage is applied while the power diode is conducting in the forward direction. Repetitive peak reverse voltage or maximum reverse voltage is the maximum allowable instantaneous value of reverse voltage repeatedly applicable. Peak forward surge current is the maximum allowable surge value of forward current without repetition. Forward voltage is the specified forward current input for power diodes. Some suppliers provide additional specifications for a high current diode, high voltage diode, power diode array, PN power diode, PN power diode array, high power diode, RF power diode, PIN power diode, switching power diode, or rectifier power diode.
IC Package Types
Power diodes use many different IC package types. Examples include: diode outline (DO), small outline diode (SOD), transistor outline (TO), small outline transistor (SOT) discrete package (DPAK), and metal electrode leadless face (MELF). DO-4, DO-5, DO-8, DO-9, DO-15, DO-27, DO-34, DO-35, DO-41 and DO-201 are diode outline (DO) packages. SOD-80, SOD-106, SOD-123, SOD-323, and SOD-523 are small outline diode (SOD) packages. TO-3, TO-66, TO-92, TO-202, TO-220, TO-237 and TO-247 are transistor outline (TO) packages. SOT23, SOT26, SOT89, SOT143, SOT223, SOT323, SOT343, SOT346, SOT353, SOT363, SOT416, SOT457, and SOT523 are small outline transistor (SOT) packages. MELF packages for power diodes include QuadroMELF, MicroMELF, and MiniMELF. D2PAK is a large surface-mounted package that includes a heat sink. SC-59, SC-74, and SC-76 are plastic, surface-mounted packages with three leads.
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Diode arrays are composed of multiple discrete (usually unconnected) diodes on a single silicon chip. Diode arrays are important semiconductor products because they save assembly time and improve reliability over individually packaged diodes. In general, diode arrays use four or more diodes in a single package.
Diodes are electronic components that conduct electric current in only one direction, functioning as a one-way valve. Diodes are manufactured using semiconductor materials such as silicon, germanium or selenium and are used as voltage regulators, signal rectifiers, oscillators and signal modulators / demodulators.
PIN diodes are three-layer semiconductor diodes consisting of an intrinsic layer separating heavily doped P and N layers. The charge stored in the intrinsic layer in conjunction with other diode parameters determines the resistance of the diode at RF and microwave frequencies.
RF diodes are designed to handle high-power radio frequency (RF) signals in stereo amplifiers, radio transmitters, television monitors, and other RF or microwave devices.
Transient Voltage Suppressor Diodes (TVS)
Transient voltage suppressor (TVS) diodes are designed to limit over-voltages. They can dissipate high amounts of transient power in a short period of time.
Tunnel diodes are heavily doped P-N diodes in which electron tunneling from the conduction band in the N-type material to the valence band in the P-type region produces a region of negative resistance. This negative-resistance region is the most important area of operation. As the voltage is increased, the current decreases. This feature makes tunneling diodes especially useful in oscillators and radio frequency (RF) applications.
Varactor diodes are p-n junction diodes that are designed to act as a voltage controlled capacitance when operated under reverse bias.