[time-nuts] power spectrum of hard limiter output

ehydra ehydra at arcor.de
Tue Jan 25 23:32:06 UTC 2011

Hi Bob -

Yes. But coming back to the CMOS inverter multi-stage amplifier:
Because of the absolute momentum signal level the first stages 
(=amplifier) sees it operates more linear than later more saturating stages.
As long as the single one stage works linear, this stage will not change 
the spectrum!
Only a little noise is added (I think adding here to the linear domain, 
but BEWARE: in later stages magnified adding into saturation regions...) 
and the signal level is improved, say 15dB. All goes linear up by 15dB here.

So we can see that indeed it is possible to move the front 'brick-wall' 
filter at least in part to following stages. How many parts??

I currently have a test-bed with three stages. All the same values. The 
question is simply: Would changing parts values for every stage to 
something individual different: would this improve the overall response 
considerable? Or is it a useless academic exercise?

- Henry

Bob Camp schrieb:
> Hi
> Most communications systems also have constraints based on signals in
> adjacent channels. That pretty much forces a solution of "lots of filter
> before lots of gain". Distributing both gain and filtering across multiple
> stages gets you into a variety of issues that map junk into the passband.
> Once the junk is there, you can't get rid of it later. 

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