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I am doing simulation using the amplifier (OPA2675). The type of the circuit: Differential Input Source V7 with label V(n004) & V8 with label V(n011). Output source R5.

Overview: As you can see in the picture my input simulation in corresponding to time, the green Sine wave is the input of the first amplifier in different amplitude. The blue sin wave is the input of the second amplifier which also have the different amplitude.

Goal: I want to draw a graph using LTspice, in this graph I want on the x axis have the Vpp of green (volt input of the first amplifier) and Vpp of the blue (volt input of the second amplifier), in order to get the relation between them and the output volt R5.

enter image description here

enter image description here

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  • \$\begingroup\$ we'll need some illustration of what you need. "Vin" is an input, which you typically specify; so there's nothing to calculate, you set that. \$\endgroup\$ Commented Nov 16, 2023 at 0:02
  • \$\begingroup\$ I removed all the unrelated tags – you don't mention any operational amplifier in your question, and this is a simulation, you can't do voltage measurements on it; it's simulated. \$\endgroup\$ Commented Nov 16, 2023 at 0:03
  • \$\begingroup\$ So my circuit is in the picture , as you can see i am using type of differential amplifier which the volt input is v7 & v8 , and now i want to measure the volt peak to peak of the voltage input of both voltage source v7 & v8 in different time domain from 0ns till 100ns , so i can Finally, plot the performance of the out voltage which is on R5 in correspondence to differences between volt peak to peak of the voltage input of both voltage source v7 & v8 in different time domain \$\endgroup\$
    – Nadine
    Commented Nov 16, 2023 at 0:25
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    \$\begingroup\$ @Hearth The only meaning I could surmise was that the OP (for reasons I don't fathom) wanted to get the peak to peak for a certain period of time for one input and a peak to peak for a different certain period of time for the other input. Can be done with .MEAS. No idea about why, though. \$\endgroup\$ Commented Nov 16, 2023 at 3:28
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    \$\begingroup\$ @Nadine I can't and won't argue, because I can do fairly interesting and complex calculations from .MEAS. Ratios of other .MEAS values, for example, and much more. I don't understand exactly why it is that you can't get what you want. But I'm not going to guess about it, either. You'll need to show me that you know how to use .MEAS and then show me what .MEAS is giving you that you don't want. \$\endgroup\$ Commented Nov 16, 2023 at 23:47

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Are you trying to put one voltage on the horizontal axis and another on the vertical axis, like this?

enter image description here

If so, all you need to do is right-click on what is normally the time axis and change the variable that appears on that axis from "time" to the signal you actually want. In the illustration I'm offering, that's V(v1). The vertical axis is determined by whatever it is you're plotting, V(out) in this case. In this particular plot, the startup conditions are shown as non-overlapping plots. Eventually the system I simulated reaches steady state, at which point every cycle overlaps, creating a dark set of overlapping traces.

A plot of this type is known as a Lissajous figure, but I'm not sure from your question if this is what you want to achieve.

As far as I can determine, LTspice only lets you choose a single horizontal variable, so if you want multiple plots of output variables against various input variables, you would need to achieve those plots individually, although you could get them all from a single simulation run—just not all at once.

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  • \$\begingroup\$ thank you but i wanted to calculate the peak to peak but is solved with the .meas equations \$\endgroup\$
    – Nadine
    Commented Nov 25, 2023 at 9:13

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