BJT Large Signal

Discussion in 'General Electronics Chat' started by Mazaag, Feb 5, 2008.

  1. Mazaag

    Thread Starter Senior Member

    Oct 23, 2004
    255
    0
    Hey guys

    Is there a value for the large signal resistance from the Collector to the emitter of a BJT ? like i know for MOSFETs there is a large signal Rds, and a small signal ro , what about BJTs ? and how do you calculate this value

    thanks
     
  2. scubasteve_911

    Senior Member

    Dec 27, 2007
    1,202
    1
    BJTs go by a Vce(sat) parameter, which is a very dynamic. It depends very much on current through the transistor and temperature.

    Steve
     
  3. mik3

    Senior Member

    Feb 4, 2008
    4,846
    63
    BJTs dont have a fixed resistance like FETs , it depends upon your circuit.

    You can find it if you devide Vce by Ic for a particular circuit
     
  4. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    The collector of a transistor is a very high impedance. The circuit's output impedance is just the collector resistor in parallel with the load resistance.
     
  5. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    Output resistance can be estimated at least for the small signal model by dividing the BJT's "Early voltage" by the collector current. Here is the wikipedia article describing this relationship.

    hgmjr
     
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