Explain briefly, the action of a transistor as a switch.

Explanation

i. the transistro is made to function in the cutt-off region and in the saturation region
ii. In the above circuit, `V_("BB") = V_(i) = I_(B) R_(B) + V_(CE) = V_("CC") - I_(C)R_(C) = V_(0)`
iii.The transistor will be in the cut-off region as long as the input voltage is less than the `V_("BE")` = 0.65V for silicon and 0.25 V for germanium. The transistor acts as an open switch
`V_(B) = V_("CC")`
iv. For a transistor operated at saturated region, `V_("CE") ~~ V_(CE) ~~ 0.` the transistor acts as a closed switch.