Why is this simple circuit un-stable?

Discussion in 'Homework Help' started by EngIntoHW, Jun 28, 2011.

  1. EngIntoHW

    Thread Starter Member

    Apr 24, 2010
    128
    0
    Hi,

    I don't understand why the following operating points are not stable:

    1.
    W=0
    X=1
    Y=0
    Z=0

    2.
    W=1
    X=0
    Y=1
    Z=1

    In both operating points, there is current flowing through R.
    Must there be no current in a stable operating point?

    Thanks.

    [​IMG]
     
  2. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,387
    1,605
    It's an astable multivibrator, it's supposed to be unstable.

    Look at state1: It may start there but C will charge thru R so Z rises to X.

    When Z rises to change W from a low to a high the real interesting things happen, can you see them?

    Hint 1: stop using 1 and 0 and use volts.

    Hint 2: Z may jump greater then the Vdd.
     
  3. EngIntoHW

    Thread Starter Member

    Apr 24, 2010
    128
    0
    Got it,
    Thank a lot mate! :)
     
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