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I was using the simple darlington circuit below as the test circuit. DC operating point analysis was run on both LTspice and Multisim, with V2 as the manipulating variable and the base voltage of Q2 as the responding variable.

After the experiment, I found out that the result were different for Multisim and LTSpice when V2 is near to zero voltage. Noted that I had modified the BJT model in Multisim to match that in LTspice.

Belows are the result of Multisim and LTspice when V2 was set to 0V and 2V respectively. For 2V, the result matched but for 0V, the result showed huge difference. Any idea causing this issue?

I have also attached the convergence/accuracy parameter lists for LTspice and Multisim.

V2 = 0V

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V2 = 2V

enter image description here enter image description here

Paramater

LTSpice

enter image description here

Multisim

enter image description here

Which one is more accurate? Is there anything I miss?

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2 Answers 2

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You have a voltmeter connected to the node in question, but only in Multisim.

The voltage difference is actually rather inconsequential in practice because it's like two leakage currents fighting. Even 1 or 2 G\$\Omega\$ input impedance on the virtual meter could cause that amount of voltage difference.

Check the voltmeter’s "internal resistance" parameter in the dialog box.

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It is more convenient to do this in time analysis. everything is very clear and understandable.enter image description here

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  • \$\begingroup\$ You can, of course, but to do this you need to restart the program, configure it in a different language, and this will take a lot of time. The language of numbers and graphs is understandable all over the world to knowledgeable people. Drawing is the language of technology, people say... \$\endgroup\$ Dec 26, 2023 at 14:57

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