Page 90 - Electrical Engineering Dictionary

n
of (a + b) . These coefficients are equal to i.e., the product of the polyphase transfer
function of the analysis and synthesis filters

n n!
= , is a pure delay. In general, the analysis and
k k!(n − k)!
synthesis filters are different, as opposed to
where n is the order of the polynomial and k the situation for an orthogonal filter bank.
is the index of the coefficient. The kth coef-
k n−k
ficient is multiplied by the term a b . biorthogonal wavelet a generalization of
orthogonal wavelet bases, where two dual ba-
binomial distribution the binomial dis- sis functions span two sets of scaling spaces,
tribution is the distribution of a random vari- V j and V j , and two sets of wavelet spaces,
ˆ
able Y that is the sum of n random variables W j and W j , with each scaling space orthog-
ˆ
that are Bernoulli distributed. ˆ
onal to the dual wavelet space, i.e., V j ⊥ W j
ˆ
Y = X 1 + X 2 + ··· + X n . and V j ⊥ W j . See also biorthogonal filter
bank.
The probability mass function of such a Y is

n k n−k BIOS See basic input–output system.
p Y (k) = p (1 − p) ,
k
bipolar (1) a type of transistor that
where p is the parameter of the Bernoulli dis-
uses both polarities of carriers (electrons and
tribution of any X i .
holes) in its operation as a junction transistor.
bioanalytical sensor a special case (2) a type of data encoding that uses both
of a chemical sensor for determining the positive and negative voltage excursions.
amount of a biochemical substance. This
type of sensor usually makes use of one bipolar device See bipolar.
of the following types of biochemical reac-
tions: enzyme-substrate, antigen-antibody, bipolar junction transistor (BJT) a
or ligand-receptor. three-terminal nonlinear device composed of
two bipolar junctions (collector-base, base-
bioluminescence See luminescence. emitter) in close proximity. In normal oper-
ation, the voltage between base and emitter
biomass General term used for wood, terminals is used to control the emitter cur-
wood wastes, sewage, cultivated herbaceous rent. The collector current either equals this
and other energy crops, and animal wastes. (with BC junction in reverse bias), or goes
into saturation (the BC junction goes into for-
biomedical sensor a device for interfac-
ward bias). Used for medium power (700 A)
ing an instrumentation system with a biolog-
and medium speed (10 kHz) applications.
ical system such as biological specimen or an
In power electronics applications, BJTs
entire organism. The device serves the func-
are typically operated as switches, in either
tion of detecting and measuring in a quanti-
their fully on or off states, to minimize losses.
tative fashion a physiological property of the
The base current flowing into the middle of
biological system.
the device controls the on–off state, where
continuous base current is required to be in
biometric verifier device that helps au-
the on state. A disadvantage is the low cur-
thenticate by measuring human characteris-
rent gain.
tics.
The base current is generally much
biorthogonal filter bank a filter bank that smaller than collector and emitter currents,
satisfies the perfect reconstruction condition, but not negligible as in MOSFETs.
c
2000 by CRC Press LLC