Q. Explain output CE characteristics?

1. In the active region ic increases slowly as Vce increases. The slope of the curved is greater than the CB output characteristics. In common emitter output characteristics the input current characteristics is constant,i.e ib is constant, but current Vc increases with Vce.

2. When Vce falls below a few tenth of a volt ,Ic decreases this occurs as Vce drops below the value of Vbe; the collector base junction then becomes forward-biased. In this region both junctions of the transistor are forward biased. The transistor is working in the saturated region. It is called saturation region because the current Ic no longer depends upon the input current Ib.

3. In the active region ,the collector current is ?dc times greater than the base current. Thus, small input current,Ib produces a large output current Ic.

4. The collector current is not zero when Ib is zero. It has a value of Iceo, the reverse leakage current. The current Iceo is related with. I_cbo by the eqn

                                  I_ceo = 1/(1-Id_c)*I_cbo

                                               Or

                                  I_ceo = (1+?_dc)I_cbo