Spice White Noise Source

In LTSpice (free from the Linear Technology web site), there are RAND and RANDOM functions which may be applied to a voltage source. I'm going to leave out a lot of details here, and you likely will have to "play around" with it to get it to do what you want, but it is possible to get random sources. You can get a Gaussian distribution with some additional fiddling around.

But...I suppose what you really want is to use a voltage source in each critical line, one at a time, and do a frequency domain small-signal analysis. That way you will determine at what frequencies the effect is important, and learn about what additional filtering you may need to apply. Often, in both simulations and in measurements, random is not the optimum excitation for learning about circuit or system performance.

Cheers, Tom

When you mentioned Gaussian distribution, it gave me an idea. I then considered less distribution. As a cheap shoot I might just string together a bunch of triangle generators at strategic frequencies. I can then insert that signal into any branch..Might be good enough..

Thanks

looking

data

In LTSpice (free from the Linear Technology web site), there are RAND and RANDOM functions which may be applied to a voltage source. I'm going to leave out a lot of details here, and you likely will have to "play around" with it to get it to do what you want, but it is possible to get random sources. You can get a Gaussian distribution with some additional fiddling around.

But...I suppose what you really want is to use a voltage source in each critical line, one at a time, and do a frequency domain small- signal analysis. That way you will determine at what frequencies the effect is important, and learn about what additional filtering you may need to apply. Often, in both simulations and in measurements, random is not the optimum excitation for learning about circuit or system performance.

Cheers, Tom

In SyMetrix Intro there is a checkbox 'enable real-time noise' for transient analysis.

That would be handy. I'll have to figure out how to do that with a behavioral block.

...Jim Thompson

You can do the same with a pulse generator too.

Colin =^.^=

Noise generators are extremely useful and would be nice if offered as a standard feature. I'm just designing a log' amp and some kind of noise source is essential for spicing to be of any value. In LTspice, I use a "behavioral voltage source" component stuck in series with the signal source I need to make noisy. Set as "V=(rand(time*1e18)-0.5)*1.0". The "1.0" gives a 1Vpp noise signal, "10e-9" for 10nV etc. john

In mixed mode, just run up a selection of PRN gens, feed the bits to a handfull of DACs and sum and multiply the outputs. pretty good white noise over a limited spectrum. goodness and spectrum width become design / cost trade offs.