static characteristics of the BJT are i) Input characteristics ii) Output characteristics iii) Transfer characteristics i) Input characteristics Input characteristic curves give the relationship between the base current ( I B ) and base to emitter voltage ( V BE ) at constant collector to emitter voltage ( V CE ) and are shown in Figure . . Initially, the collector to emitter voltage is set to a particular value (above . V to reverse bias the junction).
Then the base-emitter voltage is increased in suitable steps and the corresponding base-current is recorded. A graph is plotted with V BE along the x-axis and I B along the y-axis. The procedure is repeated for different values of V CE . fact that the emitter current I E is due to holes and the base current I B is due to electrons.
However, the current through the external circuit is due to the flow of electrons. EXAMPLE . In a transistor connected in the common base configuration, α = , I mA E = Calculate the values of I C and I B . Solution α = I C E C E × = α mA E C ∴ = − E C mA .
. Static Characteristics of Transistor in Common Emitter Mode The know-how of certain parameters like the input resistance, output resistance, and current gain of a transistor are very important for the effective use of transistors in circuits. The circuit to study the static characteristics V CE V CC V BE R R V BB I B I C I E mA _ _ _ _ _ _ C E μA Figure . NPN transistor in common emitter configuration - - - - - - - - Unit electronics and Communication r V V i BE CE = ∆ ∆ ( .
) The input impedance is high for a transistor in common emitter configuration. ii) Output characteristics The output characteristics give the relationship between the collector current ( I