DC bias

When describing a periodic function in the time domain, the DC bias, DC component, DC offset, or DC coefficient is the mean value of the waveform. If the mean amplitude is zero, there is no DC offset. In contrast, various other frequencies are analogous to superimposed AC voltages or currents, hence called AC components or AC coefficients.

The term originated in electronics, where it refers to a direct current voltage, but the concept has been extended to any representation of a waveform. The term's use is extended to two-dimensional transformations like the discrete cosine transform used in JPEG.

A waveform without a DC component is known as a DC-balanced or DC-free waveform. DC-balanced waveforms are useful in communications systems to avoid voltage imbalance problems between connected systems or components.

DC offset is usually undesirable when it causes saturation or change in the operating point of an amplifier. An electrical DC bias will not pass through a transformer; thus a simple isolation transformer can be used to block or remove it, leaving only the AC component on the other side. In signal processing terms, DC offset can be reduced in real-time by a high-pass filter. When one already has the entire waveform, subtracting the mean amplitude from each sample will remove the offset. Often, very low frequencies are called "slowly changing DC" or "baseline wander".

Bias

Bias is an inclination or outlook to present or hold a partial perspective, often accompanied by a refusal to consider the possible merits of alternative points of view. Biases are learned implicitly within cultural contexts. People may develop biases toward or against an individual, an ethnic group, a nation, a religion, a social class, a political party, theoretical paradigms and ideologies within academic domains, or a species. Biased means one-sided, lacking a neutral viewpoint, or not having an open mind. Bias can come in many forms and is related to prejudice and intuition.

In science and engineering, a bias is a systematic error.

Cognitive biases

A cognitive bias is a repeating or basic misstep in thinking, assessing, recollecting, or other cognitive processes. That is, a pattern of deviation from standards in judgment, whereby inferences may be created unreasonably. People create their own "subjective social reality" from their own perceptions, their view of the world may dictate their behaviour. Thus, cognitive biases may sometimes lead to perceptual distortion, inaccurate judgment, illogical interpretation, or what is broadly called irrationality. However some cognitive biases are taken to be adaptive, and thus may lead to success in the appropriate situation. Furthermore, cognitive biases may allow speedier choices when speed is more valuable than precision. Other cognitive biases are a "by-product" of human processing limitations, coming about because of an absence of appropriate mental mechanisms, or just from human limitations in information processing.

Biasing

Biasing in electronics is the method of establishing predetermined voltages or currents at various points of an electronic circuit for the purpose of establishing proper operating conditions in electronic components. Many electronic devices such as transistors and vacuum tubes, whose function is processing time-varying (AC) signals also require a steady (DC) current or voltage to operate correctly — a bias. The AC signal applied to them is superposed on this DC bias current or voltage. The operating point of a device, also known as bias point, quiescent point, or Q-point, is the steady-state voltage or current at a specified terminal of an active device (a transistor or vacuum tube) with no input signal applied.

The term is also used for an alternating current (AC) signal applied to some electronic devices which is similarly required for correct operation, such as the tape bias signal applied to magnetic recording heads used in magnetic tape recorders.

Overview

In electronic engineering, the term bias has the following meanings:

Bias (mythology)

In Greek mythology, Bias (/ˈbaɪ.əs/; Ancient Greek: Βίας) was a brother of Melampus who received one third of the Kingdom of Argos (see Melampus for more information).

Marriages

Bias married his cousin Pero who was the daughter of Neleus. It was said that Neleus would not allow his daughter to marry anyone unless the suitor brought him the oxen of Iphiclus. This Melampus achieved with courage and using his supernatural abilities of speaking with animals, upon winning the challenge he arranged the marriage of Pero and Bias, they had one child together, Talaus.

When Pero died Bias remarried Iphianassa, daughter of Proetus, after Melampus had cured her, her sisters and the women of Argive from madness. He received one third of Proetus's kingdom all of which he gave to Bias. Bias and Iphianassa had a daughter Anaxibia who married Pelias, to whom she bore Acastus and several daughters. According to Pausanias, Amythaon is the father of Bias and Melampus. Their mother was Idomene, daughter of Pheres or Abas of Argos.