Electronic Engineering Dictionary

Diode. A two element, solid-state device made of either germanium or silicon; it is primarily used as a switching device. A semiconductor device having two terminals and exhibiting a nonlinear voltage-current characteristic. Also Diode Manufacturers listing. An electron tube containing two electrodes: a cathode and a plate. Also see a description of different Diode Types and definitions.

Diode Tube

Semiconductor Diode Schematic Symbols

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.

Diode Limiter. A circuit that uses a diode to limit the voltage so that it does not exceed a set value.

Diode Mixer. A circuit that combines two different frequencies together using a diode as the non-linear element. Read more on Mixer Circuits.

Diode ORing. Diode ORing is normally used when two different power supplies are connected in parallel and separated by diodes so that if one supply fails the other begins to supply power to the circuit. The diodes stop one supply from feeding current into the other supply while still allowing current from either supply to feed the circuits being powered. Each leg of a diode is tied to a supply while the other sides of the diodes are connected together and to the load. The return path also have separate diodes in each leg of a return path and with the ends of other side connected together and to the return side of the load.

Diode Transistor Logic. [DTL] A style of digital logic that used both diodes and transistors to perform the logic function. Diode Transistor Logic was used up to the early to mid seventies when it was replaced by TTL logic. Diode Transistor Logic is obsolete and should not be used in new designs, it's doubtful any DTL devices could be procured in any event.

Diode Transistor Logic

DIP IC. Dual Inline Package IC. A style of Integrated Circuit that has its pins on either side of a rectangular shaped package. Normally a DIP IC refers to a through-hole component, while a surface mound device would be called an SOIC [for example]. Refer to the topic covering DIP ICs and Sockets for a graphic and additional info. Also used to refer to a particular body width or pin row width that is associated with a few of the more common DIP IC packages, when used to refer to a DIP switch for example. Commonly found DIP packages that conform to JEDEC standards use an inter-lead spacing (lead pitch) of 0.1 inch (2.54 mm). Row spacing [associated with body width] varies depending on lead counts, with 0.3 in. (7.62 mm) or 0.6 inch (15.24 mm) the most common.

DIP Switch. A switch using a Dual In-Line Package. A style of board-mount switch that has two rows of terminals running on two sides of the component. Normally used or associated with switches that could use the same pin pattern as a DIP IC, that is a DIP IC could be removed from a board or socket and a DIP switch inserted in its place. Read more on DIP Switches.

Dipole. A common type of half-wave antenna made from a straight piece of wire cut in half. Each half operates at a quarter wavelength of the output. [Antenna Terms.]

Direct Attached Storage. [DAS] Is a [digital] storage system directly attached to a server.

Direct Coupled Amplifier. A amplifier that is connected to another circuit without an intervening component, so that the DC bias of one stage effects the next stage. A DC amplifier, sometimes also called a direct current amplifier. Refer to the circuit schematic to the right. Other common coupling methods include; capacitive coupled, RC coupled and transformer coupled amplifiers.

Direct Coupling. The interconnection or coupling of two circuits either by direct means or through a resistor, so that the coupling is not frequency dependent.

Direct Current. [DC]. A current that only flows in one direction.

Direct Current Amplifier. A DC amplifier designed to amplify DC voltages. DC amplifiers are normally either resistive coupled or direct coupled.

Directional Coupler. A device that samples the energy traveling in a waveguide in one direction only.

Directivity. The ability of an antenna to radiate or receive more energy in some directions than in others. The degree of sharpness of the antenna beam.

Directly Heated Cathode. A wire, or filament, designed to emit the electrons that flow from cathode to plate. The filament is designed so that a current is passed through it; the current heats the filament to the point where electrons are emitted.

Direct Memory Access. [DMA] a means of data transfer directly between a peripheral and the system memory without passing through the CPU. A transfer of multiple bytes of data in a system, but supervisory over-head only occurs on the first byte or the start of the transfer [all other bytes are transferred directly with system control] as in a Block Transfer.

Director. The parasitic element of an array that reinforces energy coming from the driver element.

Direct Short. Same as Short Circuit.

Direct Current. [DC] An electric current that flows in one direction only. Opposite of alternating current.

Direct Wave. A transmitted wave that travels directly between the transmitting antenna and the receiving antenna. See more specific Antenna Terminology definitions.

Disc Capacitor. A small ceramic through-hole capacitor in the shape of a disc. Read more on Disc Capacitor [Dictionary of Capacitor Terms].

Discharge. The reduction of an electric charge on an object.

Discharge Rate. The rate, usually expressed in amperes or time, at which electrical current is taken from the battery.

Disciplined Oscillator. [DO] An oscillator whose output frequency is continuously steered [often via a phase locked loop] to agree with an external reference.

Disconnect Switch. In a power system, a switch used for closing, opening, or changing the connections in a circuit or system or for purposes of isolation.

Discrete Components. Individual transistors, diodes, resistors, capacitors, and inductors.

Discriminator. A circuit in which amplitude variations are derived in response to phase or frequency variations. The part of an FM receiver that extracts the desired signal from an incoming FM wave by changing frequency variations into amplitude variations.

Dish. A microwave antenna shaped like a dish. For more detail refer to the Antenna Dictionary.

Diskette. The same as a Floppy Disk, or just Floppy. A removable disk cartridge, containing a circular non-rigid [floppy] magnetic storage element which rotates in the case. The Diskette is out-dated and obsolete, replaced by USB thumb drives.

Diskette

Dispersion. The refraction of light waves that causes the different frequencies to bend at slightly different angles.

Displacement Current. The current that appears to flow through a capacitor.

Dissipative Material. A material defined as having a surface resistivity between 10⁵ and 10⁹ ohms/square.

Dissymmetry. The differential between the dwell time of the positive half cycle and the dwell time of the negative half cycle.

Distortion. Any unwanted change between an input signal and output signal. An undesired change between a transmitted signal and the received signal. Read more on Distortion.

Distributed Constants. The constants of inductance, capacitance, and resistance in a transmission line. They are spread along the entire length of the line and cannot be distinguished separately.

Distribution Amplifier. A component or equipment that accepts an input signal and outputs that signal to a number of outputs.
Read more on a Distribution Amplifier.

Distributive Law. In Boolean algebra the law which states that if a group of terms connected by like operators contains the same variable, the variable may be removed from the terms and associated with them by the appropriate sign of operation for example, A(B + C) = AB + AC.

Distributive Capacitance. The capacitance in a transmission line that is assumed to be distributed along the length of the transmission line.

DMOSFET. Depletion type metal oxide semiconductor field effect transistor.