Common base configuration:

for pap transistor connection for common base operation is as follow: common base means base is common to both input and output side of configuration. we use current direction in the direction in the direction of holes movement for common base  input or driving point characters for is transistor is the plot of the i.e. vs vibe for various level of output voltage . Output or collector characteristics for a common base configuration for various level of i.e. can be plotted as shown in figure

In the active reason the collection base junction is revised biased while the base emitter junction is forward biased.

When i.e.=0, the collector current is simply due to the reverse saturation current

(Note)L1) in the cut off region the collector base and collector  emitter junction base t of a transistor are the both reverse biased.

(11) in saturation region the collector base and base emitter junction bad are forward biased .

Alpha: in de mode the level of ice and i.e. dude to majority carriers the relative by a quantity called alpha and is defined.