To learn the transistor characteristics a transistor is either functioned in ordinary emitter pattern or in common foundation pattern. Let’s capture an NPN transistor functioned on common emitter approach. As converses previously a transistor functions barely when the input side is biased forwardly and output side is biased reversely. Ammeter is united in succession with collector & base to calculate bottom current and current of collector correspondingly. Voltmeters are united in parallel to calculate the input volt (VBE) & output volt (VCE). To learn the characteristics, the output factor, specifically VCE is held stable and the deviation of input current with input volt is calculated and the similar designed in the graph (below) (VBE v/s IB). A unit of curves might be designed by changing VCE. The graph symbolizes the characteristics of a forwardly biased P-N junction.
The incline of the graph at a specified tip provides the input resistance
Now to learn the output characteristics, input current is held even and the alternates out voltage and output current are calculated and a graph is designed (above). It symbolizes characteristics of a reversely biased P-N junction diode.
The output impedance is able to calculate from the graph. Output impedance is the quotient of output volt to output current at a stable input current.
To be precise –
The output characteristics depicts that IC alters quickly in the start but in a little while IC becomes self-regulating of VCE, appearing like a saturated one. The quotient – is almost stable and it is entitled as current gain.