what is depletion region in transistor?

Question

explain briefly adout trransistor

Answer 1

The depletion region is that part of the semiconductor in which the charge carrier density has been reduced by electrostatically attracting the carriers to the ends (source-drain, emitter-collector).

Answer 2

An NPN transistor can be considered as two diodes with a shared anode region. In typical operation, the emitter–base junction is forward biased and the base–collector junction is reverse biased. In an NPN transistor, for example, when a positive voltage is applied to the base–emitter junction, the equilibrium between thermally generated carriers and the repelling electric field of the depletion region becomes unbalanced, allowing thermally excited electrons to inject into the base region. These electrons wander (or "diffuse") through the base from the region of high concentration near the emitter towards the region of low concentration near the collector. The electrons in the base are called minority carriers because the base is doped p-type which would make holes the majority carrier in the base.

The base region of the transistor must be made thin, so that carriers can diffuse across it in much less time than the semiconductor's minority carrier lifetime, to minimize the percentage of carriers that recombine before reaching the collector–base junction. The thickness of the base should be less than the diffusion length of the electrons. The collector–base junction is reverse-biased, so little electron injection occurs from the collector to the base, but electrons that diffuse through the base towards the collector are swept into the collector by the electric field in the depletion region of the collector–base junction.
The collector–emitter current can be viewed as being controlled by the base–emitter current (current control), or by the base–emitter voltage (voltage control). These views are related by the current–voltage relation of the base–emitter junction, which is just the usual exponential current–voltage curve of a p-n junction (diode).

The physical explanation for collector current is the amount of minority-carrier charge in the base region. Detailed models of transistor action, such as the Gummel–Poon model, account for this charge explicitly to explain transistor behavior more exactly. The charge-control view easily handles photo-transistors, where minority carriers in the base region are created by the absorption of photons, and handles the dynamics of turn-off, or recovery time, which depends on charge in the base region recombining. However, since base charge is not a signal that is visible at the terminals, the current- and voltage-control views are usually used in circuit design and analysis.

In linear circuit design, the current-control view is often preferred, since it is approximately linear. That is, the collector current is approximately 'beta' times the base current. The voltage-control model requires an exponential function to be taken into account.

Answer 3

When the p and n type semiconductors are joined together .The majority carriers from each type of semiconductor move to the opposite semiconductor.For e.g the electrons from the n-type move to the p type.Similarly , the holes from p-type move to the n type. Since the atoms lose electrons and holes they become ionised.For e.g the atoms in the n type lose one of their valence electrons (which acts as the majority charge carrier) and the atom becomes positively charged.Similarly , the atoms in the p side lose their holes and become negatively charged.Therefore , close to the junction immobile ions are formed .These positive and negative ions near the junction set up a potential called barrier potential. This region consisting of these ions which constitutes the barrier potential is called depletion region .

https://www.electrikals.com/

Answer 4

It is the nutral region which forms at the junction of two opposit polarity semiconductors.