I am trying to build my own EFT generator (IEC 610000-4-4). A person online had done some design and they have calculated the values of the components in order to make the circuit. I used LTSpice to simulate their component values and see what results I get. I am not using a switch as required by the standard for now, I just want to simulate one pulse.

enter image description here

What is wrong with my circuit? How come I see such a low value at the output?

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    \$\begingroup\$ Did you mean to have a switch between the DC source and the pulse output? If this is for practical purposes, mind that you will need quite an excellent switch to do this. \$\endgroup\$ Feb 6 at 19:58
  • \$\begingroup\$ Yes indeed, I agree 100% with you the topology of the switch will have to be very good, but for now I just want to start with that :). \$\endgroup\$ Feb 6 at 20:09

1 Answer 1


The voltage at the output is low because you've got a DC voltage and a capacitor, which blocks DC, in series with the output.

You will only see a significant voltage there when the input voltage changes.

You could change the voltage source to a pulse, then you would see an output.

Here I've changed it to a pulse, changed the simulation settings and added a couple of options to get better accuracy. enter image description here

  • \$\begingroup\$ what are the parameters that you selected for the pulse? \$\endgroup\$ Feb 6 at 22:18
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    \$\begingroup\$ @DimitarZhekov Vinitial 0, Von 2000, Tdelay 1m, Trise 1p,Ton 5. I made Ton 5 before I shortened the simulation time, so it could be reduced to 2m, but it doesn't matter, I just wanted it to start low, go high after 1 mSec, and then stay high. You'll need to adjust the pulse to mimic whatever you are driving the circuit with. Note that when the input pulse goes low you'll get a negative going pulse from the output. \$\endgroup\$
    – GodJihyo
    Feb 6 at 22:28
  • \$\begingroup\$ Perfect ! Thanks \$\endgroup\$ Feb 7 at 14:59

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