emitter resistance in BJT

Thread Starter

electricShOcK

Joined Apr 15, 2009
3
Hi all, I am confused that in a BJT does the emmiter resistance have any effect on Ic and Vce? Does it make the BJT go into active mode? I tried graphing Re against Ic and Vce and the graphs were complete opposite to each other! Any help please!!!:eek:
 

Audioguru

Joined Dec 20, 2007
11,248
If the base of a transistor has a voltage divider providing the base with a fixed voltage then the emitter voltage is about 0.7V less and is also fixed.
Ohm's Law says that a low value resistor with a fixed voltage has a high current through it. A high value resistor with the same fixed voltage has a low current.
Ohm's Law also applies to the current in the collector resistor and since the collector current is the same as the emitter current then changing the value of the emitter resistor changes the collector current.

When the collector current changes then the collector voltage (Vce) changes.
 
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