Common emitter configuration:

even in common emitter configuration current relation is like is same like common bias configuration. For common emitter configuration output characteristic is ice vs. vice for an range of a value of input current in above note is not =0 whine is zero

In the activity region of common emitter amplifier the collector emitter amplifier junction is reverse biased while the biased emitter bias junction is forward biased.

Common collector configuration: it is primarily used for impedance matching since it has high input impendence and low output impedance opposite yo that of common bias and common bias emitter configuration. Common bias emitter configuration.