H parameter model help

Discussion in 'Homework Help' started by jinkazama99, Jul 15, 2010.

  1. jinkazama99

    Thread Starter New Member

    Jul 15, 2010
    3
    0
    circuit.jpg
    Ok, so according to the notes that i waas given, it says hie is 900 ohms, and the two bias resistors are 60K ohms and parallel to each other, so they make insignificance difference to others, so the 2 bias resistors can be ignored...i thought 60k is very big resistance 0_o??
    and the resistance of
    1/hoe is 450k ohms, which is over 100 times the combined resistance of Rload and Rc, therefore hoe can also be discarded...

    So, i think what he really means is that if one of the combined resistance is much larger than the h parameter values, we simply ignore it??
     
  2. jinkazama99

    Thread Starter New Member

    Jul 15, 2010
    3
    0
    Sorry i mean if the combined resistance is much bigger than the others, than we can discard the bigger value resistance.
    like on the RHS of the circuit hoe's resistance is much higher than Rc||Rl, so we discard hoe.
     
  3. jinkazama99

    Thread Starter New Member

    Jul 15, 2010
    3
    0
    oh i think its because the resistance are so high that almost no current passes through them, so we ignore them.
     
  4. Jony130

    AAC Fanatic!

    Feb 17, 2009
    3,957
    1,097
    Your conclusion is quite correct.
    For example if we connect two resistors in parallel, First 1K and second 100K.
    The equivalent resistance is equal Rz = 1K||100K = 990Ω
    And that why we can sometime ignore larger component of a resistance.

    We have very similarly situation in series connection resistance
    Rz = 1K+100K = 101KΩ but now we can ignore the small resistance.
     
Loading...