What Determines the 0.2V Saturation Voltage in BJTs?

[mikey12]

Hi,
This is my first post in the forum. :)

Why is the saturation voltage of a transistor equal to 0.2 V? Why not a lesser value?
During saturation the base is filled with majority carriers and the barrier potential is absent. Hence the voltage should be 0V, right?

 

[es1]

It's not always 0.2V. That's just a rule of thumb. For example, see this part:
http://www.onsemi.com/PowerSolutions/product.do?id=NSS12201LAs you implied, changing the geometry, doping, current and temp of the BJT can effect Vce(sat).