Bias (electrical engineering)
electrical engineering, the term bias has the following meanings:
# A systematic deviation of a value from a reference value.
# The amount by which the average of a
setof values departs from a reference value.
# Electrical, mechanical, magnetic, or other force (field) applied to a device to establish a reference level to operate the device.
telegraphsignaling systems, the development of a positive or negative DC voltageat a point on a line that should remain at a specified reference level, such as zero.
:"Note:" A bias may be applied or produced by (i) the electrical characteristics of the line, (ii) the
terminal equipment, and (iii) the signaling scheme.
Federal Standard 1037Cand from MIL-STD-188)
Most often, bias simply refers to a fixed DC voltage applied to the same point in a circuit as an AC signal, frequently to select the desired operating response of a semiconductor or other electronic component (forward or reverse bias). For example, a bias
voltageis applied to a transistorin an electronic amplifierto allow the transistor to operate in a particular region of its transconductancecurve; a (much higher) bias voltageis also often applied to the grid electrodes in a vacuum tubefor precisely the same reason.
A hot bias can lower the tube life span, but a "cool" biased can induce
Bias is also the term used for a high-frequency signal added to the audio signal recorded on
magnetic tape. See tape bias.
Bias is used in
direct broadcast satellites such as DirecTVand Dish Network, the IRDbox actually powers the feedhornor LNB receiver mounted on the dish arm. This bias is changed from a lower voltage to a higher voltage to select the polarizationof the LNB, so that it receives signals that are polarized either clockwiseor counterclockwise, thereby allowing it to receive twice as many channels.
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