I am trying to achieve this plot in LTspice from the datasheet of LT1762. (I am a beginner trying to understand how this works) enter image description here

My schematic is as follows: enter image description here

The output I get is this. enter image description here

What am I doing wrong?

  • \$\begingroup\$ My main goal is to try to plot Dropout Voltage vs. Output Current . I cannot figure out what I am doing wrong. \$\endgroup\$ Commented Aug 11, 2023 at 5:45
  • \$\begingroup\$ What is the Y-axis in your simulation result? \$\endgroup\$
    – sai
    Commented Aug 11, 2023 at 10:05
  • \$\begingroup\$ it was V(in,out) i.e the difference in the input and output voltages. \$\endgroup\$ Commented Aug 11, 2023 at 10:11
  • \$\begingroup\$ I am getting similar error while plotting the quiescent current vs input voltage graph. \$\endgroup\$ Commented Aug 11, 2023 at 10:23

2 Answers 2


The problem is with the .step temp -50 125 50 command. What this command will do is run a series of plots from -50\$^\circ\$C to 125\$^\circ\$C in 50\$^\circ\$C steps. Each value in a .step command is discrete and will run the simulation over again plotting another trace in a new color with just that parameter changed, it is not a continuous sweep like a DC sweep. While the .step command editor will let you set a 'sweep' with temp as the parameter it will not give you a continuous variable to plot against. If you change the Y axis to plot temp it will show you the initial value \$\pm\$0.1 as you can see on your graph.

In order to recreate the original chart you would need to sweep the temperature and plot with that as the Y axis, I'm not aware of a way to do this in LTspice, there may not be a way. I believe the temperature parameter has to be set at the beginning of a simulation sweep and can not be changed mid sweep, you can only step it over multiple sweeps.

Also in your other .step command I think you can leave out dec, that's for doing a logarithmic step by decade and requires a lower limit, upper limit, and the number of steps per decade as parameters whereas you have a list of values.


I tried the same circuit at my end and I get 2.5V output. I did the DC sweep analysis instead. You can see the output below:

enter image description here


Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.