"A"
"B"
"C",
"D",
"E",
"F",
"G",
"H",
"I",
"J",
"K",
"L",
"M",
"N",
"O",
"P",
"Q",
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"T",
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"W",
"X",
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"Z"
Previous set of "F" terms and definitions.
FIELD. The electromagnet which furnishes the magnetic field that interacts with the armature in motors
and generators.
| FIELD-EFFECT TRANSISTOR (FET). A transistor consisting of a source, a gate, and a drain. Current flow is controlled by the transverse electric field under the gate. A transistor in which the conduction is due entirely to the flow of majority carriers through a conduction channel controlled by an electric field arising from a voltage applied between the gate and source terminals. [FET Manufacturers] |
![]() JFET |
FIELD EXCITATION. The creation of a steady magnetic field within the field windings by the application of a dc voltage either from the generator itself or from an external source.
FIELD OF FORCE. A term used to describe the total force exerted by an action-at-a-distance phenomenon such as gravity upon matter, electric charges acting upon electric charges, and magnetic forces acting upon other magnets or magnetic materials.
FILAMENT. The cathode of a thermionic tube, usually a wire or ribbon, which is heated by current passing through it. Also refer to the listing on Vacuum Tube.
FILM ICs. Conductive or non-conductive material deposited on a glass or ceramic substrate. Used for passive circuit components, resistors, and capacitors.
FILTER. A selective network of resistors, capacitors, and inductors that offers comparatively little opposition to certain frequencies, while blocking or attenuating other frequencies. In electronics, a device that transmits only part of the incident energy and may thereby change the spectral distribution of energy: (a) high-pass filters transmit energy above a certain frequency; (b) low-pass filters transmit energy below a certain frequency; (c) bandpass filters transmit energy of a certain bandwidth; (d) band-stop filters transmit energy outside a specific frequency band. Refer to the entry on Passive Filters.

Low Pass PI Filter
| FILTER RESPONSE. The output response of an active or passive filter. Refer to the definition of Filter for the different types. The graph shows the different orders of a Butterworth Filter, 1st order filter to fifth order. | ![]() Butterworth Filter |
FINAL POWER AMPLIFIER (FPA). The final stage of amplification in a transmitter.
FIRMWARE. A software program which is permanently stored in Non-Volatile Memory [ROM].
FIRST DETECTOR. See MIXER.
FIXED BIAS. A constant value of bias voltage.
FIXED RESISTOR. A resistor having a definite resistance value that cannot be adjusted. Also refer to Resistor Definitions. Resistor Manufacturers
FIXED SPARK GAP. A device used to discharge the pulse-forming network. A trigger pulse ionizes the air between two contacts to initiate the discharge.
FLAG. In data transmission or processing, an indicator, such as a signal, symbol, character, or digit, used for identification. A flag may be a byte, word, mark, group mark, or letter that signals the occurrence of some condition or event, such as the end of a word, block, or message. Also see Protocol Definitions
FLAT LINE. A transmission line that has no standing waves. This line requires no special timing devices to transfer maximum power.
FLAT PACK. An IC package. IC Package Type Definitions
FLEMING VALVE. A two-electrode vacuum tube used as a detector. Also refer to the listing on Vacuum Tubes.
FLEXIBLE COAXIAL LINE. A line made with an inner conductor that consists of flexible wire insulated from the outer conductor by a solid, continuous insulating material. Refer to the Definition of Coax Cable. Manufacturers of Coax Cable
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