whatbias conditions must be present for the normal operation of a transistor amplifier?

 

Volume III Chapter 4 of All About Circuits answers this question far more eloquently than I can.

http://www.allaboutcircuits.com/vol_3/chpt_4/index.html

Enjoy!

 

what is the direction of the current in the transistor?? consider both NPN and PNP

 

Depends on one's definition of "current."

http://www.allaboutcircuits.com/vol_1/chpt_1/7.html