Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Thevenin Equivalent for circuits with dependent sources

  1. Jan 28, 2009 #1

    Good day! I was studying Circuit Theorems when I stumbled upon this circuit that has a dependent current source asking for a Thevenin equivalent. Up until now, I was only familiar with solving circuits with independent sources so this has me having a hard time. I tried using superposition theorem to solve for Vth but my answers don't match with the given answers. Can anyone please help me with this? Here is the pic for the circuit.

    http://img230.imageshack.us/img230/3359/picture1um7.th.jpg [Broken]

    Thanks in advance!

    Attached Files:

    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. Jan 28, 2009 #2
    Did you do KCL at node X (where the dependent current source is going into)? Can you see the relationship of voltage at this node to the current going out of the node? (Ix going into 3 and 4 ohms)
  4. Jan 30, 2009 #3
    First I would remove the sources and solve for the Rth.

    Next I would use Node-Voltage analysis on the original circuit:
    -use the node on the negative side of the voltage source as your reference node
    -now the only nodes with unknown voltages are the upper-middle node and upper-right node, label as V1 and V2, respectively.
    -write the constraint equation for Ix
    -write the KCL equations for nodes V1 and V2
    -solving these 3 equations for the 3 unknowns should give you the information needed to find this circuit’s Vth

    I hope that helps you get the correct answer, and that I described it correctly :bugeye:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook