emitter resistance in BJT

Discussion in 'Homework Help' started by electricShOcK, Apr 15, 2009.

  1. electricShOcK

    Thread Starter New Member

    Apr 15, 2009
    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:
  2. Audioguru

    New Member

    Dec 20, 2007
    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.