How can I simulate the gaussian distribution

mingche_joe · July 7, 2025, 8:26am

Hi ,

How can I simulate the gaussian distribution (normal distribution in Qspice). I came accross this post while searching the method
Simulating tran noise with QSPICE - QSPICE - Qorvo Tech Forum

I have plotted the histogram of the method in the post. However, it does not look like the normal distribution to me.

PyQSPICE

ivan1 · July 7, 2025, 7:20pm

Here is how you simulate gaussuan distribution.

Best regards

mingche_joe · July 8, 2025, 2:53am

Hi Ivan,

Thank you for the solution. Is there any way I can do it in the transient analysis? I want to see how my circuit react to noise.

Regards,
Joe

tobalt · July 8, 2025, 9:09am

(post deleted by author)

tobalt · July 8, 2025, 9:19am

This is a workaround, by adding 6 random calls to make gaussian look alike distribution.

V=random(time)-random(time+17)+random(time+27)-random(time+37)+random(time+47)-random(time+57)

KSKelvin · July 8, 2025, 3:48pm

This is the best I can think of in generating a gaussian distribution in .tran and can follow gaussian distribution in regardless simulation time.

SrcGaussian.qsym (2.2 KB)
example.SrcGaussian.qsch (3.2 KB)

** if you enable .option seedclock, it can generate new set of random number in each simulation run.

Here is netlist of this .subckt for your reference

.subckt X1•SrcGaussian Y0+ Y0- Y1+ Y1-
B1 U1 0 V=limit(random(1e15*time/V(divider)+1e15*random()),1m,0.999)
B2 U2 0 V=limit(random(1e15*time/V(divider)+1e15*random()),1m,0.999)
B3 Z0 0 V=sqrt(-2.0*log(V(U1)))*cos(2.0*3.14159*V(U2))
B4 Z1 0 V=sqrt(-2.0*log(V(U1)))*sin(2.0*3.14159*V(U2))
B5 Y0+ Y0- V=mean + std * V(Z0)
B6 Y1+ Y1- V=mean + std * V(Z1)
B7 divider 0 V=pow(10,floor(log10(time)))
.ends SrcGaussian