18WuD2x

296 form • forward voltage drop
form 1. The core or frame upon which an inductor
is wound. 2. A vessel, such as a mold, used in the
shaping stage of a manufacturing process.
formaldehyde Formula, HCHO. A colorless, pungent
gas that is a constituent of many well-known
plastic insulating materials (see PHENOLFORM-
ALDEHYDE PLASTICS).
formant 1. The audio-frequency range in which
the sound of a spoken syllable is concentrated. 2.
Any general group of audio frequencies.
formant filter In an electronic organ, an audio filter
that changes the waveshape of a tone so that
the tone will have the desired characteristics.
format 1. The form in which data is presented
(e.g., the arrangement of characters, fields,
words, totals, etc.). 2. To prepare a computer disk
or tape so that it will accept data.
form factor 1. The SHAPE FACTOR for a filter or
tuned circuit. 2. For a half-cycle of an alternating-current
(ac) quantity, the ratio of the rootmean-square
(rms) value to the average value.
form feed 1. A mechanical system that positions
paper being supplied to a line printer. 2. The FF
character that initiates advancement of printout
paper in a printer. 3. The advancement of printout
paper in a printer.
form feed character In a control loop, a character
(symbol, FF) used on printing devices for controlling
form feed.
forming See ELECTROFORM, 1.
form stop An automatic device that stops a printer
when the paper runs out.
FORTH A high-level computer programming language
used in certain robots, automated factories,
medical electronic devices, and electronic
games. It was originally developed in the 1970s to
facilitate computer control of equipment in astronomical
observatories.
FORTRAN A high-level computer programming
language developed in the 1950s, and still used
in some scientific and mathematical applications.
It is not especially useful for the control of electronic
or mechanical devices.
fortuitous conductor A medium that creates an
unwanted electrical path.
fortuitous distortion Waveform distortion that results
from causes other than characteristic effects
or bias effects.
forward AGC Automatic gain control provided by
special transistors whose transconductance decreases
with increasing emitter current, and vice
versa. Compare REVERSE AGC.
forward-backward counter A counter that runs
forward to perform addition and backward to perform
subtraction.
forward bias Forward voltage or current in a transistor
or semiconductor diode.
forward-blocking state For a silicon-controlled
rectifier, the off state, during which the forward
bias is so much less than the forward breakover
voltage that only small off-state current flows.
forward breakover voltage 1. For a semiconductor
pn junction, the smallest forward voltage at
which appreciable conduction occurs. This is
about 0.3 V for germanium and 0.6 V for silicon.
2. For a silicon-controlled rectifier, the forward
voltage value at which the device abruptly
switches on.
forward characteristic The current-voltage response
of a semiconductor junction that is biased
in the forward (high-conduction) direction. Compare
REVERSE CHARACTERISTIC.
forward compatibility standards Standards developed
to make programs for one computer system
usable for additional or replacement equipment.
forward conduction The increased current conduction
through a pn junction that is forward biased.
Compare REVERSE CONDUCTION.
forward current Symbol, I f . The increase in current
flow through a pn junction that is forward biased.
Compare REVERSE CURRENT.
forward current-transfer ratio The current gain of
a bipolar transistor (alpha for the common-base
connection and beta for the common-emitter connection).
forward power 1. In a transmission line, the power
leaving the generating source, as measured by a
directional wattmeter at that location. 2. The
power arriving at the load at the terminating end
of a transmission line.
forward propagation by ionospheric scatter See
FORWARD SCATTER.
forward propagation by tropospheric scatter Abbreviation,
FPTS. A method of transmitting part
of a radio signal beyond the horizon using the
scattering effect of the troposphere. Also see FOR-
WARD SCATTER and TROPOSPHERE.
forward resistance Symbol, R f . The resistance of a
forward-biased pn junction. Also see FORWARD
BIAS. Compare REVERSE RESISTANCE.
forward-reverse ratio See FRONT-TO-BACK RA-
TIO.
forward scatter Also called forward propagation by
ionospheric scatter. The scattering of a radio wave
in the normal direction of propagation to points
beyond the skip zone. The phenomenon occurs
because of waves returned from regions in the
ionosphere. Compare BACK SCATTER.
forward transconductance Symbol, g fs . For a
common-source-connected FET, the ratio of a
drain-current differential to the differential of
gate-to-source voltage that produces it; g fs =
1000(dI D /dV GS ), where g fs is in microsiemens, I D is
the drain current in milliamperes, and V GS is the
gate-to-source voltage in volts.
forward voltage Symbol, E f or V f . Voltage whose
polarity causes maximum current to flow through
a pn junction. Compare REVERSE VOLTAGE.
forward voltage drop The voltage across a semiconductor
junction that is biased in the forward
(high-conduction) direction. Compare REVERSE
VOLTAGE DROP.