[SOLVED] DC Sweep of hysteretic device in LTSpice

Hi,

I am trying to obtain the I-V curve of a device with hysteretic behavior. That is, when the voltage goes from high to low and from low to high, the current curve is not overlapped. I wrote the following dc analysis condition in my code:

.DC Vtest -2V, 2V, 0.1V

But this will only sweep from -2V to 2V. How to write this line so that the voltage will also sweep backwards (from 2V to -2V)?

Thanks in advance,
-Guangyu

.DC vtest 2, -2, -0.1

Another option is to use a very slow triangular wave in a transient analysis.

Keith

Keith,

Thank you. Is it possible to plot I-V curve for both directions? It seems I cannot put both '.DC Vtest -2, 2, 0.1' and '.DC vtest 2, -2, -0.1' in the netlist.

-Guangyu

You could run two sweeps I guess. You may have to use parameter sweeps. I am not sure of the exact syntax with LTspice though. I tend to use a slow transient analysis with a triangular wave input - it seems easier.

Keith.

A slow transient ramp sure will be a lot more like test conditions.
You should be able to change the waveform plot X-axis from time
to v(input_node) and see a hysteretic "voltage waveform"

Sometimes it is convenient to run two instances of the test
cell in the same schematic especially if you want to do math
on results - using controlled sources to look at (say) input
difference becomes possible rather than having to post-process.

You could also do crazy things like setting the circuit up to
chatter freely and use a low pass filter feedback with (say)
one instance set to 10% supply and one set to 90% supply,
put a small HF sinusoid (>> Tpd, << filter) in series with a
(limited) vcvs and you can get quasi-DC results for VILH,
VIHL and HYST from endpoint node voltages.

I could not figure out how to change the x-axis from time to voltage in LTspice. Is it possible to plot an i-v curve under transient analysis? If not, I will retrieve the data and plot in other waveform tools. Thank you a lot!

-Guangyu