Electronic Engineering Dictionary

Emergency Power. Temporary source of limited electrical power used upon the loss of the normal power source.

EMF. [Electromotive Force] The force that causes electricity to flow between two points with different electrical charges or when there is a difference of potential between the two points. The unit of measurement is volts.

Emitter. [E] The element in a transistor that emits current carriers (electrons or holes). [Transistor Definitions, Transistor Manufacturers]. Transistor graphic, Common Emitter Circuit, showing bias currents and voltage drops between terminals. The cathode in vacuum tube.

Transistor Emitter

Emitter Coupled Logic. [ECL] See ECL. For more detail on switching speed, ECL circuit diagram and logic family comparisons refer to ECL IC Manufacturers.

Emitter Follower. A buffer. A transistor circuit that reproduces the input signal, in phase but at something less than unity gain [characterized by a high input impedance and a low output impedance]. A transistor circuit that uses the emitter as the output which follows the input of the Base voltage, minus a diode drop. A Common Collector Amplifier [shown to the right] because the collector terminal is common to both the input and output side of the circuit [Vcc in this case]. The Emitter follower has a high input impedance and a low output impedance.

Emitter-Injection Modulation. The transistor equivalent of the cathode modulator. The gain is varied by changing the voltage on the emitter.

Emphasis. In FM transmission, the intentional alteration of the amplitude-vs-frequency characteristics of the signal to reduce adverse effects of noise in a communication system.

Enable Line. An input to a logic function that enables or disables the output signal. An Enable line may be active high or active low, and may be indicated by the abbreviation of OE for Output Enable. The 54125 to the right shows the [active low] enable line as [C] which disables or Tri-states the output into a high-impedance or OFF-state.

Enamel. A synthetic compound of cellulose acetate (wood pulp and magnesium). Used to insulate wire in meters, relays, and motor windings.

Enameled Wire. A wire coated with an insulated material.

Encapsulated. Embedded in solid material or enclosed in glass or metal.

Encapsulation. In open systems, the technique used by layered protocols in which a lower layer protocol accepts a message from a higher layer protocol and places it in the data portion of a frame in the lower layer. A protective coating of plastic or other material applied over components [also refer to Potting]. A process for encasing a part or an assembly of discrete parts within a protective material which is generally not over 2.5 mm thick and does not require a mold or container.

Enclosure. A housing for electronic equipment or components, as in an Electronic Chassis or speaker enclosure.

Encode. To use a code to represent individual characters in a message. Here are a number of Encoding Terms. To convert data by the use of a code, frequently one consisting of binary numbers, in such a manner that re-conversion to the original form is possible.

Encoder. A device used to encode a signal or character from one format to another. Example IC Encoder; 74HCT147, 10-to-4 line priority encoder. Encoder Schematic. Also refer to Manufacturers of Optical Encoders, or Manufacturers of Linear Encoders.

Encoding. The process of translating data from one form to another.

End Node. A node that is the ultimate producer or consumer of a data networks service; the transmitter or receiver of a message.

End of Life. A part or device is no longer being manufactured, however there may or may not be inventory still in stock or carried by a distributor. Also refer to Component Life Cycle Definition, or Obsolete Parts Distributors.

End of Frame. [EOF] A character used to indicate that the last of the frame has been transmitted. The last Transmitted word of a Frame.

End of Message. [EOM] The last character in a fixed length message. The absence of data for a certain amount of time.

End of Transmission. [EOT] An ASCII Code character used to indicate the End of Transmission. A character used to indicate the conclusion of a transmission that may have included one or more texts and any associated message headings.

Energized. (hot, live) Electrically connected to a source of potential difference, or electrically charged so as to have a potential significantly different from that of earth in the vicinity.

Energy. The ability or capacity to do work.

Enhancement-Mode FET. A FET having substantially zero channel conductivity for zero gate to source voltage. The channel conductivity may be increased by the application of a gate to source voltage of appropriate polarity.

Enhancement-Mode Operation. The operation of a FET such that changing the gate to source voltage from zero to a finite value increases the magnitude of the drain current.

Envelope Detector. A circuit that functions to detect the outer envelope of a waveform, as in a Transistor AM Envelope Detector.

Ephemeris. A table showing the pre-calculated position of a satellite at any given time.

Ep-Ip CURVE. The characteristic curve of an electron tube used to graphically depict the relationship between plate voltage (Ep) and plate current (Ip).

Epitaxial Growth. The growth of one crystal on the surface of another crystal. The growth of the deposited crystal is oriented by the lattice structure of the original crystal.

Epitaxial Process. A method of depositing a thin, uniformly doped crystalline region (layer) on a substrate.

EPROM. An Erasable PROM [Programmable Read Only Memory]. Read more; EPROM Definition, Manufacturers of EPROMs.

Equalization. The process of compensating for distortion within a circuit by adding additional networks that compensate for any gain that was lost or increased over some frequency band.

Equalizer. A component or network that provides equalization by correcting, or compensating for frequency related undesired amplitude changes which have occurred within the system. Also refer to a Op Amp Equalizer Design.

Equatorial Orbit. An orbit that occurs when the plane of a satellite coincides with the plane of the earth at the equator. [Graphic on right side-bar]

Equipment. A general term characterizing the broad category of electronic items (units,subsystems,systems,etc.).

Equivalent Resistance. [Req] A resistance that represents the total ohmic values of a circuit component or group of circuit components. Usually drawn as a single resistor in a simplified circuit.

Equivalent Series Resistance. [ESR] All the series resistances [R, Xc, Xl] in a component treated as a single resistance [at a particular frequency].

Erasable Programmable Read Only Memory. See EPROM Definition. Memory that is erased by an electrical signal or ultraviolet light.

ERP. See Effective Radiated Power as part of the Antenna Dictionary.

Error. Refer to the page covering Error Terms.