Alternative way of measuring characteristic current through diode in LTSpice without using current probe

Question

I'm new to LTspice so I would like to have a few ideas. Here is a circuit:

Basically, the output of BLOCK_1 is a small triangular waveform. I need to pass this output through a 1N4148 diode which is a test device. The current which I get through it is:

Essentially, this is what I obtain after using the current probe of LTspice.

I've been thinking of a situation where I am not allowed to use the current probe, for instance.

In that case, I need the I/V characteristic for the diode D3 using the voltage probe only.

In that case, should I just add a capacitor in parallel with D3? I just need to add a single component to get both I and V characteristics of D3, I have a hunch.

I would probably need to probe two node voltages to make that work. I need to figure out those 2 nodes and plot one against the other in LTSpice to be sure, but I've been unable to do so.

Somehow, I need to know the Shockley characteristic current for D3 without using the current probe. Can someone please help me out in this with a nice explanation?

IMPORTANT: I would be building the circuit on a circuit board and probing it with an oscilloscope, so I won't be able to probe the current. That's why I need a way around.

Answer 1

How do I do that if I connect a resistor in series to D3?

Like this:

^{simulate this circuit – Schematic created using CircuitLab}

Then Channel 1 will give you the voltage across the diode

Channel 2 will give you the current through the diode

As Rsense has a small value, the voltage across it will be very small. So much smaller than the voltage across the diode that you can ignore it (assume it is zero).

If you're nit-picking then use the subtract function on the oscilloscope and subtract the voltages: Vdiode = Vch1 - Vch2

Maybe the current through the diode is small making the voltage across Rsense also small. Then simply use a larger value for Rsense, like 10 ohms or even 100 ohms.

Aim to keep the voltage across Rsense below 100 mV so that the diode voltage will not be affected much by that voltage.