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The Shockley diode equation relates the diode current of a p-n junction diode to the diode voltage .This relationship is the diode I-V characteristic: = (), where is the saturation current or scale current of the diode (the magnitude of the current that flows for negative in excess of a few , typically 10 −12 A).
Under reverse bias, the diode equation's exponential term is near 0, so the current is near the somewhat constant reverse current value (roughly a picoampere for silicon diodes or a microampere for germanium diodes, [1] although this is obviously a function of size).
Its collector and base are tied together, so its collector-base voltage is zero. Consequently, the voltage drop across Q 1 is V BE, that is, this voltage is set by the diode law and Q 1 is said to be diode connected. (See also Ebers-Moll model.) It is important to have Q 1 in the circuit instead of a simple diode, because Q 1 sets V BE for ...
The saturation current (or scale current), more accurately the reverse saturation current, is the part of the reverse current in a semiconductor diode caused by diffusion of minority carriers from the neutral regions to the depletion region. This current is almost independent of the reverse voltage. [1]
Diffusion current is a current in a semiconductor caused by the diffusion of charge carriers (electrons and/or electron holes).This is the current which is due to the transport of charges occurring because of non-uniform concentration of charged particles in a semiconductor.
Depending on the material and the degree of detail desired, a variety of energy levels will be plotted against position: E F or μ: Although it is not a band quantity, the Fermi level (total chemical potential of electrons) is a crucial level in the band diagram. The Fermi level is set by the device's electrodes.
A small-signal model is an AC equivalent circuit in which the nonlinear circuit elements are replaced by linear elements whose values are given by the first-order (linear) approximation of their characteristic curve near the bias point.
Besides impedance, Miller arrangement can modify the IV characteristic of an arbitrary element. The circuit of a diode log converter is an example of a non-linear virtually zeroed resistance where the logarithmic forward IV curve of a diode is transformed to a vertical straight line overlapping the axis. Not constant coefficient.