Amplifier is a functioning by which the amplitude of variation of ac signal voltage / current/ power can be enhanced

(i) Principle and circuit diagram: The amplifying action of the triode is based on the fact that small change in grid voltage produces the similar change in the grid voltage as because of a large change in the plate voltage. A circuit for triode as an amplifier

(ii) Working: First of all the mutual characteristic curves of a triode to be used as an amplifier is plotted and the grid potential - Corresponding to the mid-point of straight portion of characteristic curve is noted.