For transistor action,which of the following statements are correct `:`
(a) Base, emitter and collector regions should have similar size and doping concentrations.
(b) The base region must be very thin and lightly doped.
(c ) The emitter junction is forward biased and collector junction is reverser biased.
(d) Both the emitter junction as well as the collector junction are forward baised.

Answer

b

Explanation

(b ) and ( c). For a transistor `beta= ( I_(C ))/( I_(B))`
`I_(B) = ( I_(C ))/( beta) ` (or ) `R_("input")= (V_("input"))/( V_(B)) =(V_("input"))/( I_(C))= beta,` i.e., `R_("input ")prop (I)/( I_(C ))`
Therefore `R_("input")` is inversly proportional to the collector current. For high collector curren, the `R_("input") ` should be small for which the base region must be very thin and lightly doped for a transistor action, the emitter junction is forward biased and collector junction is reverse biased.