[sdiy] Popcorn Noise Generator?

[Ray Wilson]

I don't know. I'm just quoting Frederiksen who seems to indicate that it is 
related to the entire circuit since he mentions abrupt changes in input 
current. I assume he means in the differential input circuitry.

I'll bet someone else on this list knows though. Stay tuned...

Ray
----- Original Message ----- 
From: "drheqx" <drheqx at heqx.com>
To: "'Ray Wilson'" <raywilson at comcast.net>; "'harrybissell'" 
<harrybissell at prodigy.net>; "'Glen'" <mclilith at charter.net>
Cc: <synth-diy at dropmix.xs4all.nl>
Sent: Saturday, July 09, 2005 7:45 AM
Subject: RE: [sdiy] Popcorn Noise Generator?


> Ray,
> Is it limited to Op Amps? I was under the impression that all silicon
> junctions would produce this type of noise when biased on.
>
> heqx
>
>>For people who are wondering what popcorn noise is...
>
>>Quote from "INTUITIVE IC OP AMPS FROM BASICS TO USEFUL APPLICATIONS"
> (not
>>shouting the title really is all caps)
>>Author: Thomas M.Frederiksen
>>National Semiconductor Technology Series
>>Copyright 1984 Thomas M.Frederiksen
>
>>START QUOTE
>>"Popcorn" Noise. A peculiar additional ac noise mechanism is sometimes
> seen
>>when an oscilloscope is used to observe the output ac noise voltage of
> an >op
>>amp. Digital signalling from outer space seeme to be taking place.
> Pulses
>>can exist with widths of many milliseconds where the constant baseline
> of
>>random ac noise abruptly steps up by a large enough factor (say, 5:1)
> to
>>trace out a rectangular pulse, with the baseline ac noise now occuring
>>across the top of this pulse, as shown in figure 3-30. This abrupt type
> of
>>noise is called popcorn noise because of the sound it makes coming from
> a
>>loudspeaker. Popcorn noise is caused by a defect that is dependent on
> the >IC
>>manufacturing technique.
>
>>This ac noise results from abrubpt changes in the input current between
> the
>>normal level and a second, qusistable level that differs by
> approximately
>>100 pA. Evidence of popcorn noise is closely monitored by the
> manufacturer.
>>however to guarantee that it is not present requires special, time
>>consuming
>>(and therefore expensive) testing.
>>END QUOTE
>
> Testing and manufacturing techniques, I'm certain, have come a long way
> in
> 21 years so I'd bet this is not as prevalent as it used to be.
>
> Cheers
>
> Ray
>
>
>
>
>
> ----- Original Message ----- 
> From: "Ray Wilson" <raywilson at comcast.net>
> To: "harrybissell" <harrybissell at prodigy.net>; "Glen"
> <mclilith at charter.net>
> Cc: <synth-diy at dropmix.xs4all.nl>
> Sent: Saturday, July 09, 2005 6:27 AM
> Subject: Re: [sdiy] Popcorn Noise Generator?
>
>
>> The grainy noise generator is white noise through a window comparator.
> The
>> window is adjustable so you get a few clicks or a lot of clicks.
>>
>> Ray
>>
>> ----- Original Message ----- 
>> From: "Glen" <mclilith at charter.net>
>> To: "harrybissell" <harrybissell at prodigy.net>
>> Cc: <synth-diy at dropmix.xs4all.nl>
>> Sent: Friday, July 08, 2005 8:40 PM
>> Subject: Re: [sdiy] Popcorn Noise Generator?
>>
>>
>>> At 10:14 PM 7/8/2005, harrybissell wrote:
>>>
>>>>how about start with white noise, then rub it into an active diode
>>>>section biased so that only peaks above a DC level would be passed.
>>>>
>>>>Those peaks would still be analog (of varying amplitude) but would
> become
>>>>less frequent as the DC level was increased.
>>>>
>>>>alternately you could get an old Gershon Kingsley record and have
> some
>>>>REAL popcorn noise...
>>>>
>>>>H^) harry
>>>
>>> What about feeding white noise through a narrow window comparator?
> That
>>> would make all the spikes the same amplitude, but is that really what
> we
>>> would want, if trying to generate popcorn noise?
>>>
>>> What about a weak radioactive source, and a Geiger Mueller tube?
>>>
>>> What about sampling the voltage drop across a blinky neon lamp?
>>>
>>> I'm just wondering. I have to admit that I'm not totally sure what
>>> isolated popcorn noise sounds like. I've heard a few audio amps which
>
>>> popped and cracked due to a circuit failure, but I don't know if
> that's
>>> really popcorn noise.
>>>
>>> Does anyone have a reference wav sample of the stuff?
>>>
>>> thanks,
>>> Glen
>>
>
>
>
>
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