Emitter is heavily doped and moderate in size.

Base is lightly doped and thin in size.

Collector is lightly doped and large in size.

Collector is moderately doped and large in size.

OR

NOR

NAND

AND

Holes are majority carriers and trivalent atoms are the dopants.

Electrons are minority carriers and pentavalent atoms are the dopants.

Electrons are majority carriers and trivalent atoms are the dopants.

Holes are minority carriers and pentavalent atoms are the dopants.

$A=0, B=0, Y=0$

$A=0, B=1 ; Y=0$

$A=1, B=0, Y=0$

$A=1, B=1 ; Y=0$