[sdiy] Popcorn Noise Generator?

[drheqx]

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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