Spice White Noise Source

[D from BC]

Where's the spice noise generator?

[In mechanics, you can whack it to see how stable it is.]

I'm thought about testing a spice circuit by injecting noise.
This would simulate dirty power rails and emi in. (Assume
filtering limitions.)

I googled & no luck yet on spice and noise injection.
(Usually when I can't find something, it often means I'm looking
for something highly original or really stupid )

Maybe my spice program is old and missing the noise gen..
Maybe spice testing like this is not done..Perhaps too many data
points...

Maybe I have to put a gain block on a noisey spice part...

 

[Tom Bruhns]

Where's the spice noise generator?

[In mechanics, you can whack it to see how stable it is.]

I'm thought about testing a spice circuit by injecting noise.
This would simulate dirty power rails and emi in. (Assume
filtering limitions.)

I googled & no luck yet on spice and noise injection.
(Usually when I can't find something, it often means I'm looking
for something highly original or really stupid )

Maybe my spice program is old and missing the noise gen..
Maybe spice testing like this is not done..Perhaps too many data
points...

Maybe I have to put a gain block on a noisey spice part...

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

 

[D from BC]

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

Where's the spice noise generator?

[In mechanics, you can whack it to see how stable it is.]

I'm thought about testing a spice circuit by injecting noise.
This would simulate dirty power rails and emi in. (Assume
filtering limitions.)

I googled & no luck yet on spice and noise injection.
(Usually when I can't find something, it often means I'm looking
for something highly original or really stupid )

Maybe my spice program is old and missing the noise gen..
Maybe spice testing like this is not done..Perhaps too many data
points...

Maybe I have to put a gain block on a noisey spice part...

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

..

 

[Ban]

Where's the spice noise generator?

[In mechanics, you can whack it to see how stable it is.]

I'm thought about testing a spice circuit by injecting noise.
This would simulate dirty power rails and emi in. (Assume
filtering limitions.)

I googled & no luck yet on spice and noise injection.
(Usually when I can't find something, it often means I'm looking
for something highly original or really stupid )

Maybe my spice program is old and missing the noise gen..
Maybe spice testing like this is not done..Perhaps too many data
points...

Maybe I have to put a gain block on a noisey spice part...

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

 

[Jim Thompson]

Where's the spice noise generator?

[In mechanics, you can whack it to see how stable it is.]

I'm thought about testing a spice circuit by injecting noise.
This would simulate dirty power rails and emi in. (Assume
filtering limitions.)

I googled & no luck yet on spice and noise injection.
(Usually when I can't find something, it often means I'm looking
for something highly original or really stupid )

Maybe my spice program is old and missing the noise gen..
Maybe spice testing like this is not done..Perhaps too many data
points...

Maybe I have to put a gain block on a noisey spice part...

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

 

[colin]

Where's the spice noise generator?

[In mechanics, you can whack it to see how stable it is.]

You can do the same with a pulse generator too.

Colin =^.^=

 

[john jardine]

Where's the spice noise generator?

[In mechanics, you can whack it to see how stable it is.]

I'm thought about testing a spice circuit by injecting noise.
This would simulate dirty power rails and emi in. (Assume
filtering limitions.)

I googled & no luck yet on spice and noise injection.
(Usually when I can't find something, it often means I'm looking
for something highly original or really stupid )

Maybe my spice program is old and missing the noise gen..
Maybe spice testing like this is not done..Perhaps too many data
points...

Maybe I have to put a gain block on a noisey spice part...

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

 

[joseph2k]

Where's the spice noise generator?

[In mechanics, you can whack it to see how stable it is.]

I'm thought about testing a spice circuit by injecting noise.
This would simulate dirty power rails and emi in. (Assume
filtering limitions.)

I googled & no luck yet on spice and noise injection.
(Usually when I can't find something, it often means I'm looking
for something highly original or really stupid )

Maybe my spice program is old and missing the noise gen..
Maybe spice testing like this is not done..Perhaps too many data
points...

Maybe I have to put a gain block on a noisey spice part...

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

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.