I know basic electronics but am totally unable to understand the Emitter-Follower configuration of transistor. Can anybody explain it in easy to understand terms? Consider the following scenario:
-I give a NPN transistor a base voltage of +5V. Voltage at collector is +12V and Emitter is connected to common ground. There is NO LOAD. (I know that if there is load on the collector side the transistor will simply act as a switch.) But if I'm not wrong, when there is no load, the voltage between Emitter and Ground is 4.2V (5V - Voltage Drop), and not 12V (or 11.2V accounting for drop)! Why is this happening? When the transistor is saturated, shouldn't current flow from Collector to Emitter and voltage should be 12/11.2 V?
-Also, the primary application of this config is to change high input impedance to low output impedance. However I am unable to understand impedance at all!
Any help will be highly appreciated. Sorry if the questions are too silly.