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Nikhil M

02/14/2022, 4:06 PM
Hello Guys, Has anyone encountered this error before on NGSPICE. I am trying to do a transient simulation of a current sensor No. of Data Rows : 0 doAnalyses: TRAN: Timestep too small; initial timepoint: cause unrecorded. Attaching a snippet of the circuit below
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Pranav Lulu

02/14/2022, 4:09 PM
@User Increase the time step in . trans command if you are performing transient simulation
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Nikhil M

02/14/2022, 4:10 PM
Hi @User its at 0.1ms will increase to 0.5ms and check
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Pranav Lulu

02/14/2022, 4:10 PM
And what is the step size?
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Nikhil M

02/14/2022, 4:10 PM
Tran is for 1ms with step size of 0.1 ms
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Pranav Lulu

02/14/2022, 4:11 PM
You should give start time stop time and then step
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Nikhil M

02/14/2022, 4:23 PM
I think there is a syntax with just step and stop time. Trying with <start stop step>
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@User i tried with a start time still the same problem
I read online i might have to give the capacitor some initial charge to avoid this any idea how i can do that?
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Pranav Lulu

02/14/2022, 4:36 PM
You have given pulse input. I can see the time in usec . Try to do trans simulation in usec
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Nikhil M

02/14/2022, 4:37 PM
Trying it .
However should that cause a problem different order of magnitude in Tran and pulse sources
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Pranav Lulu

02/14/2022, 4:46 PM
Yes I guess..
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Nikhil M

02/14/2022, 4:56 PM
I tried still the same I think it has something to do with the capacitor I removed it to check what will happen
Its not able to find the DC bias point its failing because of that i need to check why DC setup is failing
@User I played around a little and looks like the issue was with some of the transistors in my comparator since the input signals came through a power transistor ngspice was not able to calculate the dc bias and failed. I manually set the gate voltages to zero and it worked fine
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Pranav Lulu

02/16/2022, 3:34 AM
Great 👍
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