# Nonlinear circuit v(i) function for I-V plot

I'm trying to understand how to theoretically derive the equation that could be used for plotting the I-V graph. The points of interest are Out + and Out - and the current that would flow through that branch if different loads were applied.

simulate this circuit – Schematic created using CircuitLab

I know that the graph should roughly resemble the image below:

After learning that Thevenin can only be used on linear circuits, I got left without ideas.

Is it possible to theoretically approach this and have a function u_out(i_out) as a result?

• What do you want to analyze/simulate now? The current source on the right? That's purely artificial, these elements aren't present in a real-world solar cell, so it makes no sense to muse about their characteristics. – Janka Oct 15 '16 at 18:56
• @Janka Changed it to have no more notion about the solar cell for it isn't the question essence. I am looking for a way how to approach getting an function which would result in a IV plot. – TheMeaningfulEngineer Oct 15 '16 at 19:14
• Then put an adjustable voltage source to the left and measure the current flowing into that source. If you want a scope reading, put the scope in xy mode, use a sawtooth voltage source and measure the drop over a series resistor. – Janka Oct 15 '16 at 19:24
• Please read the question again. In the first sentence I address the goal and motivation for the question. I'm trying to understand how to theoretically derive the equation – TheMeaningfulEngineer Oct 15 '16 at 19:33
• Then, the answer is: The circuit is that of a diode paralleled by a current source. Voltage over the diode is governed only by the diode characteristics and the current (set by lighting intensity). All equations are that of a silicium diode. Look up the formulas of the silicium diode. – Janka Oct 15 '16 at 19:37