Nodal Analysis Problem (Matlab and PSpice Output Included)

Discussion in 'Homework Help' started by smithc2005, Oct 2, 2009.

  1. smithc2005

    Thread Starter New Member

    Oct 2, 2009
    1
    0
    I have to solve for V0 , using nodal analysis. I am getting different answers in matlab and PSPICE. The circuit is below
    [​IMG]

    2 supernodes ; or 1 big supernode Here are my nodal equations:

    v1-v3 = 12
    v3 - v2 = 6

    (v3)/6k + (v1)/4k - 6/k = 0

    Matlab output is here:

    Code ( (Unknown Language)):
    1. A=[1,0,-1;0,-1,1;.004,0,.006]
    2. b=[12;6;.006]
    3. format long
    4. inv(A)*b
    5.  
    6. A =
    7.  
    8.     1.0000         0   -1.0000
    9.          0   -1.0000    1.0000
    10.     0.0040         0    0.0060
    11.  
    12.  
    13. b =
    14.  
    15.    12.0000
    16.     6.0000
    17.     0.0060
    18.  
    19.  
    20. ans =
    21.  
    22.    7.799999999999999
    23.  -10.200000000000001
    24.   -4.200000000000001
    PSPICE Schematic:
    [​IMG]

    So confused!!!!
     
    Last edited: Oct 2, 2009
  2. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    5,448
    782
    A couple of your matrix terms look wrong - you should have values like 1/4000 = .00025 and 1/6000 = 0.000167 there somewhere.
     
  3. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    5,448
    782
    BTW - the PSPICE worked correctly.
     
  4. Tesla23

    Active Member

    May 10, 2009
    318
    67
    To doublecheck just use superposition and you can pretty well write down the solution:

    Vo = -6/10*12 + 0 + 4/10*36 = ?
     
  5. kaankarabulut

    New Member

    Oct 3, 2009
    3
    0
    7.2v is correct one. probably your equ is wrong
     
  6. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    5,448
    782
    Starting equations were correct but Matlab stuff should be like this ....


    -->A
    A =

    1. 0. - 1.
    0. - 1. 1.
    0.00025 0. 0.0001667

    -->b
    b =

    12.
    6.
    0.006

    -->inv(A)*b
    ans =

    19.2
    1.2
    7.2
     
Loading...