Transistor as an Amplifier

Transistor as an Amplifier An amplifier circuit I B = base current I C = collector current I E = emitter current V BB = base voltage V CC = collector voltage The function of resistant R B is to control and limit the base current. How transistors function as an amplifier: • The forward-bias from base to emitter narrows the base- emitter, BE depletion laer. • The reverse-bias from base to collector widens the base- collector, BC depletion laer. • The free electrons from emitter diffuse easil through the fo biased BE !unction into the p -tpe region. • The base region is lightl doped and ver thin, so it has a l number of holes. Therefore, onl a small percentage of the all ele flowing through BE !unction can combine with the available holes in th base region. • "ost of the electrons do not combine with holes but diffuse into BC depletion laer. • #nce here, these electrons are pulled through the reverse- biased BC !unction b the electric field set up b the force of attr between the positive and negative ions.

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Transcript of Transistor as an Amplifier

An amplifier circuit

IB= base currentIC= collector currentIE= emitter currentVBB= base voltageVCC=collector voltage

The function of resistantRBis to control and limit the base current.

How transistors function as an amplifier: The forward-bias from base to emitter narrows the base-emitter,BEdepletion layer. The reverse-bias from base to collector widens the base-collector,BCdepletion layer. The free electrons from emitter diffuse easily through the forward-biasedBEjunction into thep-type region. The base region is lightly doped and very thin, so it has a limited number of holes. Therefore, only a small percentage of the all electrons flowing throughBEjunction can combine with the available holes in the base region. Most of the electrons do not combine with holes but diffuse intoBCdepletion layer. Once here, these electrons are pulled through the reverse-biasedBCjunction by the electric field set up by the force of attraction between the positive and negative ions. Electrons now move through the collector region and into the positive terminal of the collector voltage source. This forms collector current which is larger than the base current.