How Would you Analyze this Nonlinear Circuit...

Discussion in 'General Electronics Chat' started by Pulsed, Sep 26, 2012.

  1. Pulsed

    Thread Starter Member

    Sep 10, 2012
    41
    3
    Here is a circuit that I have been struggling with.

    So we have two Ideal Resistors (with their perfect characteristics attached below), two 4.7k Resistors, two DC voltage sources and one AC voltage source with a 9v triangular wave the peak the waveform is 9v.

    I want to calculate:

    (1) - The maximum positive voltage that can appear at 'v'.

    (2) - The maximum negative voltage that can appear at 'v' .

    (3) - The maximum current that can pass through D1

    (4) - The max current through D2

    I know the answers to the first two, but I dont understand the methodology.

    So do we convert the circuit into an equivalent Thévenin/Norton circuit?

    How would you analyze it?

     
  2. Pulsed

    Thread Starter Member

    Sep 10, 2012
    41
    3
    Dear all,

    I have solved this question on my own, but I still would like to know if my 'methodology' is correct, if someone could just overview this? Is this the proper route to take? Is there a smoother method (thévenin/Norton)?

    OK, so we start with the Circuit diagram in the original post. We replace the AC voltage source with a positive 9V potential.
    From that circuit we can see that the voltage at node e is given by the equation:

    e = (4.7k*9V)/(47+47) = 4.5v.

    From this we can deduce that the diode D1 is forward biased with a potential of 2.25v and D2 is reverse biased with a voltage of 2.5v.

    A perfect forward biased diode can be replaced with a short, and a perfect reverse biased diode can be replaced with an open circuit (diode characteristics attached in the original post).

    So doing that we come up with the second, 'simplified', circuit attached.

    Using the method of superposition, we come to the following conclusions. The voltage at node e is actually 2.25v.

    So this solves the first question:

    "(1) - The maximum positive voltage that can appear at 'v'."

    Next, using Kirchhoff's current law, we can form the following equation.

    I1+ID+I3=0 or ((2.25-9v)/4.7k)+(2.25/4.7k)= ID = 9.57e-4

    Which solves the third question:

    "(2) - The maximum negative voltage that can appear at 'v' ."

    We then do the whole thing again, except use a -9v source.

    Is this correct thinking from an engineering perspective?

    Many thanks in advance.
     
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