Electronic – Circuit Analysis with an ideal diode

circuit analysisdiodes

I'am trying to solve this problem using superposition but can't seem to get the right answer.

The problem is to look for the voltage in R3 in the following circuit:

  • The V1 graph is green
  • The R3 voltage graph is red.
  • (The red graph, R3's voltage, goes up to about 11V and stays there
    until the .5ms and then goes down to at about -71V)

I used LTSpice to find the voltage in R3 and it came out to be this:

Could someone tell me what technique to use and how to start please.

Edit 1: It was hard to see the R3 voltage graph colored blue, so changed it to red.

Best Answer

Depending whether the diode is in the conducting or non-conducting state, your circuit could have two different equivalent circuits:

schematic

simulate this circuit – Schematic created using CircuitLab

A is the equivalent circuit when the diode is conductiong. B is the equivalent circuit when the diode is not conducting.

You should be able to see that solving Vout is trivial in case A.

In case B you can solve using mesh analysis, or using modified node analysis. Superposition could be applied, but is not needed.

Then you must examine the solution for case B and find any situations where the diode would not be biased correctly to be non-conducting, and replace the solution at those points in time with the solution from case A.

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