Diode. A diode is a two terminal device using a PN junction. Diodes may be made from Silicon, Germanium, Selenium, or Gallium Arsenide. Most diodes will be made of Silicon. Normally a forward voltage drop of 0.7 volts will be seen with Silicon Diodes, and a forward voltage drop of 0.3 volts will be seen with Germanium Diodes.
Diodes are primarily used as switching devices and for converting ac voltages to dc voltages. [Diode Manufacturers]. Diode types:
Diode Array. A group of diodes contained with in a single semiconductor package [possible Package Styles]. The diodes within the package may be isolated from one another or interconnected in any number of configurations. For example; a package may contain a number of diodes with all the cathodes [common cathode], or anodes [common anode] connected together. More detail on Diode Arrays.
Avalanche Diode. A diode designed to operate around the avalanche breakdown region.
Barritt Diode. [Barrier injection transit time diode] Operate similarly to IMPATT diodes. The operating frequencies are determined by the transit times across the drift. Used for barrier injection transit time diodes. Also found as Baritt Diode.
Bridge Rectifier. A circuit or component consisting of 4 separate diodes which function as a full wave rectifier. Although a two diode circuit is also considered a bridge rectifier. Read more on a 4-Diode Bridge Rectifier.
Diode Detector. A demodulator that uses one or more diodes to provide a rectified output with an average value that is proportional to the original modulation. A device which converts rf energy into dc or video output.
Forward Voltage Drop. The voltage drop across the diode when current is flowing through the diode in the forward direction. The typical voltage drop is 0.7 volts.
Germanium Photodiode: A germanium-based PN- or PIN-junction photodiode. Germanium-based detectors are noisier than silicon-based detectors. Silicon-based detectors are therefore usually preferred for shorter wavelengths.
Glass Diode. A diode having a body made of glass and not some other material.
Gunn Diode. A microwave diode that exhibits negative resistance arising from the bulk negative differential conductivity occurring in several compound semiconductors such as gallium arsenide, and that operates at a frequency determined by the transit time of charge bunches formed by this negative differential conductivity.
Injection Laser Diode. [ILD] A laser that uses a forward-biased semiconductor junction as the active medium.
Impact Diode. IMPact ionization Avalanche Transit-Time [IMPATT] Diode. A semiconductor microwave diode that, when its junction is biased into avalanche, exhibits a negative resistance over a frequency range determined by the transit time of charge carriers through the depletion region.
Laser Diode: A type of Light Emitting Diode; also see Laser Diode manufacturers.
Light Emitting Diode: 'LED', A PN-junction diode that emits visible light when it is forward biased. Depending on the material used to make the diode, the light may be red, green, or amber. More LED Terms, [LED Manufacturers]
MIM Diode. A junction diode with a thin insulating layer of material sandwiched between two metallic surface layers which operates as a tunneling diode.
Nickel-Oxide Film Diode: A diode that made using Nickel-Oxide Film.
PIN Diode:[Positive-Intrinsic-Negative Diode]. A diode with a large intrinsic (I) region sandwiched between the P- and N- doped semiconducting regions. A PIN diode appears as an almost pure resistance at RF and in some cases used as an attenuator. Read a bit more on PIN Diodes as part of the Radar Dictionary. A 1N5719 is an example of a general purpose PIN diode, in an axial lead package.
Photodiode: Operated in reverse-bias, reverse current increases 'almost' linearly with increase in incident light
Point-Contact Diode. A diode in which the end of a fine wire is pressed against a semiconductor. This style of construction is also called a Cats whisker or crystal diode, although both of these terms are dated [but not out-dated], and also don't always imply a Point-Contact Diode.
Rectifier Diode: Heavy duty [high current] diode used to convert AC to DC. Bridge Rectifier Circuit definition.
Schottky Barrier Diode: The Schottky barrier diode is a simple metal-semiconductor boundary with no P-N junction. A depletion region between the metal contact and the doped semiconductor region offers little capacitance at microwave frequencies.
Schottky Diode: A Schottky Diode is designed with a rapid turn on and off once the threshold voltage is reached.
Semiconductor Diode. A semiconductor device having two terminals and exhibiting a nonlinear voltage current characteristic.
Shockley Diode. A four layer pnpn semiconductor diode.
Silicon Photodiode: A silicon-based PN- or PIN junction photodiode. Such photodiodes are useful for direct detection of optical wavelengths shorter than approximately 1 um.
Step Recovery Diode. A pn junction active solid-state device in which a forward bias voltage injects charge carriers across the junction but prior to recombination of the carriers, a reverse voltage is applied to return the charge carriers to their source as a group.
Tunnel Diode: Has a negative resistance region. The current through the diode increases up to a certain voltage, than with increasing voltage the current decreases until a voltage point is reached and the current begins to increase again.
Varactor Diode: 'Varicap' or 'VVC', Voltage [dependent] variable capacitor [varies in picofarads]. A two terminal semiconductor device in which use is made of the property that its capacitance varies with the applied voltage. [Varactor Diode Manufacturers]
Varistor: Resistance [flow of current] changes as a function of applied voltage voltage. A varistor may also be called a VDR [Voltage Dependent Resistor]. Varistors will have a negative voltage coefficient [high resistance at low voltages and a low resistance at high voltages]. [Varistor Manufacturers ]
Zener Diode: Designed to conduct in the reverse [bias] direction: with a precise breakdown voltage [Vz].
Detailed Zener Diode Definition, or [Zener Diode Manufacturers]
Metal Oxide Varistor: [MOV] A resistor that changes value with applied voltage. A varistor may also be called a VDR [Voltage Dependent Resistor]. Varistors will have a negative voltage coefficient. MOV devices are used in parallel with the load. [Varistor Manufacturers]
Peak forward anode voltage: The peak forward anode voltage is the maximum voltage applied to the anode with respect to the cathode in the forward direction.
Peak inverse anode voltage. The peak inverse anode voltage is the maximum voltage applied to the anode with respect to the cathode in the inverse direction.
Transient Voltage Suppressor: 'TVS', Designed to absorb a transient over-voltage. The device may be designed as Uni-Polar device protecting in one direction or a Bi-Polar device protecting the circuit in both directions. TVS manufacturers are listed on the Transient Voltage Suppressor page [Nonlinear Resistor Manufacturers]. TVS devices are used in parallel with the load. 16-pin Uni-Polar or Bi-Polar TVS components in a DIP package.
Definitions by Application:
Clamping Diode: A diode used to limit the peak voltage on a line to a pre-determined maximum voltage. An older term was a catching diode.
Damper Diode: A diode implemented to reduce voltage spikes. The diode is normally positioned anti-parallel [cathode to collector, anode to emitter] across a Collector-Emitter junction of a transistor. In high-speed circuits a separate damper diode is employed, while low-speed circuits might use a transistor having an integrated damper diode on the same silicon. The process of integrating the two devices together tends to speed up of the recovery time of the diode which negates its purpose in high speed systems. Damper diodes are used in deflection circuits for example.
Detector Diode: A device which converts rf energy into dc or video output.
Microwave Diode: A two terminal device that is responsive in the microwave region of the electromagnetic spectrum, commonly regarded as extending from 1 GHz to 300 GHz.
Mixer Diode: A microwave diode that combines rf signals at two frequencies to generate an rf signal at a third frequency. For example the RF diode mixers 1N53, 1N78, and the 1N82 are used as a UHF Diode Mixer. Read more on Mixer Circuits.
Rectifier Diode: A diode used to convert alternating current [AC] to direct current [DC], although the DC will be pulsating DC [at the frequency of the AC, unless there is additional filtering to smooth the variations in the DC voltage. A number of diodes are sold as rectifier diodes; including 1N5614, 1N5616 and so on.
Schottky Diode Mixer: A Schottky diode used as a nonlinear element having a low noise figure and nearly square law characteristics.
Voltage-Reference Diode: A diode which is normally biased to operate in the breakdown region of its voltage-current characteristic and which develops across its terminals a reference voltage of specified accuracy, when biased to operate throughout a specified current and temperature range.
Welding Diode: A diode with a very large forward current rating.