[SI-LIST] Re: HSpice noise analysis question

Mike,

I'm going to make a guess because I haven't done a noise analysis in
SPICE in recent memory.

My understanding is that SPICE first determines the total output noise.
Then, because many analog designers are more interested in the noise
referred to the input, it applies the input>output transfer function, to
find what the equivalent input-referred noise would be.

In your case with no input, you don't care what the input-referred noise
is.  You could use just any voltage source, even one not connected to
the rest of the circuit ... except that you wouldn't want something like
a zero voltage gain (transfer function) from there to your output
(possible divide-by-zero errors?).

Try something like the DC power voltage source, which likely has some
non-zero transfer function to the output node.  You just want it to run
without errors.  Then ignore the input-referred results.

Or even better, add a dummy zero-valued voltage source in series with
your output node, and use that.

Regards,
Andy

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