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I want to add two different ground potentials in my LTspice model, one for the power stage and the other for the control signal coming from a function generator and gate driver of a MOSFET.

I am new to LTspice so I don't know how this is done. Can anyone here help me?

I want to have the ground points highlighted in yellow at a different potential from the ground points marked in red.

I wanted to have ground points highlighted with yellow at different potential then ground points marked by red

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  • \$\begingroup\$ can you draw an schematic by hand or with the built-in tool in this site about what exactly you want to achieve? I mean, in general, the grounds of those 2 devices will meet somewhere, right? \$\endgroup\$
    – Designalog
    Jan 30, 2023 at 7:47
  • \$\begingroup\$ You only get to call one (and exactly one) net as 'ground.' You can use a 'jumper' in LTspice to connect a different net to the ground net, if that's what you want to do. Otherwise, what do you want to do? I'm then confused. \$\endgroup\$ Jan 30, 2023 at 8:04
  • \$\begingroup\$ @ErnestoG I have added my spice schematic. I wanted to have ground points highlighted with yellow at different potential then ground points marked by red \$\endgroup\$
    – Alison
    Jan 30, 2023 at 8:04
  • \$\begingroup\$ @periblepsis I have added my schematic and I wanted to have ground points highlighted with yellow at different potential then ground points marked by red. I used the other method by using option of Net Label and using COM as second ground to ground gate driver pin but doing so the gate driver is not working. I dont understand what you said about jumper \$\endgroup\$
    – Alison
    Jan 30, 2023 at 8:12
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    \$\begingroup\$ @Alison You're not going to be able to have those points at different potential, you have U1 powered by the 15V source labeled Vcc, so you'll want the ground for that IC to be the same as the ground for that voltage source. You could connect GND and COM together, but then there's no point of having them separate in the first place. \$\endgroup\$
    – GodJihyo
    Jan 30, 2023 at 8:20

1 Answer 1

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There's only one ground in LTspice, which is Node 0. If you want a second common point for part of the circuit you could use a named net.

Select Label Net from the toolbar or edit menu, or hit F4. This will bring up a dialog where you can select COM, which will give you an alternate common symbol, or you can type in a name for a net and select which type (none, input, output, bi-directional) it is. Click OK and it will give you a symbol to place on the schematic. Use this symbol for all of the points you want to be your second ground. Note that if you want to probe voltages relative to this new net you will need to set it as the the reference after running your simulation by right clicking it and selecting Mark Reference. This net will then be used as the reference (think black multimeter lead) for the voltage probe until you run the simulation again when you would need to set it again.

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