Output tension in the scheme with the emitter is the collector tension measured rather emitter electrode. In order that collector transition was closed, tension of a has to be big in size, than the direct tension of base.
In transistors as one of independent variables choose the emitter current which is easier giving in to regulation, than tension. From characteristics the greatest distribution of a entrance and output characteristics of the transistor.
If current of the emitter is equal to zero, itself the characteristic of electron-hole transition: in a chain of a collector small own return current of IKO or taking into account equality (IKBO current proceeds. At Ueb=0 own return current of a collector
With growth of current of the emitter intensity of an internal field of base, the movement of holes on the collector becomes more directed, as a result recombinational losses on a base surface, increases transfer, and consequently, and. At further increase in current of the emitter the coefficient of injection decreases and grow to decrease by a volume recombination therefore the coefficient of transfer of current.
When giving direct tension on base emitter transition and to chains of base opens there is a recombinational component of current. Base current in this mode according to expression; at increase in direct tension it decreases to zero in the beginning, and then changes the direction and almost exponential according to a ratio (
At decrease in collector tension to size, smaller base tension, collector transition that would have to cause increase in current of base opens, but on a condition it has to be constant. For maintenance of current of base at the set level it is necessary to reduce the base tension that is followed by reduction of currents of the emitter and a collector therefore output at have sharp recession. The transistor in the mode of saturation at which nonbasic carriers of a charge are injected in base not only emitter, but also collector transition Effective management of current thus significantly decreases, the base current coefficient sharply decreases.
Entrance tension in the scheme with the general emitter is the base tension measured rather emitter. In order that emitter it was open, base tension to be negative (the r-n-r transistor is considered).
At the considerable size of current of the emitter the coefficient of transfer of current of base starts falling due to decrease in coefficient of injection, reduction of the effective area of the emitter and increase in recombinational losses in volume of base.
At the base current equal to zero that takes place at a small tension of base when the recombinational component of current of base is equal to the return current of collector transition. collector current according to expression (1
When giving on the collector of the return tension its current increases due to emergence of own current of a collector of IKB0 and some increase in coefficient of transfer of v, reduction of thickness of base a little.
If in a chain of the emitter some current of Ie is created, already at a tension of a collector in its chain according to expression (Ik=i'E current caused by injection of holes from the emitter proceeds. As this current is caused by a gradient of concentration of holes in base, for its maintenance of collector tension it is not required.
From a formula (2 the physical sense of tension follows: it has to have such size that the current of injection of collector transition created by it completely the collector transition arriving current of injection of emitter transition as, on a condition, the resulting collector current.