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power amp driver block topology?
power amp driver block topology?
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Old 19th September 2003, 04:44 PM   #111
Christer is offline Christer  Sweden
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Location: Sweden
Default Documents on noise from the noise on the net

I am not sure if there were anyone else than jam, Bricolo and
me being interested in the noise theory and the question John
challenged us with, but for those of us who are interested and
didn't already know all about it I went hunting on the net and,
contrary to my previous attempts, managed to find some good
documents on amplifier and semiconductor noise. So those
who wish to learn more about the basic theory may find some
of the following documents helpful:

(deals with noise on amplifier level and defines the basic
theory needed for this)

(defines and discusses noise sources in semiconductor devices)

(actually a compilation of diagrams and formulae on various
things, but also briefly defines the basic types of noise.)

(Another document discussing referral of noise sources to the
input, also covered in the National app note).

These documents resolve some of my previous confusion, at
least, since I falsely assumed it would be possible to arrive at
an answer to Johns question from the info he gave us. I now
realize he probably didn't mean that, since it seems we have
to make assumptions about the load resistance/impedance in
the two cases to be able to do a noise referral.

I also wasn't sure if the theory John presented dealt also with
burst and flicker noise. Checking with these documents shows
that not to be the case. An interesting question is thus whether
these noise mechanisms must also be considered or if they
can be ignored for audio purposes? One paper actually claims
burst noise to often be the dominant factor in JFETs and flicker
noise in MOSFETs.

Finally, I'd like to say that Johns question, and especially the
follow-up question, show great pedagogical insight. Thanks
for bothering about it.
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Old 19th September 2003, 08:14 PM   #112
Joe Berry is offline Joe Berry  United States
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Default Re: Re: going by the book

Originally posted by mikek
I fear you've taken the remarks in Solomons paper out of their proper context...
Well, it's clear that I'm unable to be helpful in this situation. I hope you find the answers you are seeking.
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Old 19th September 2003, 08:55 PM   #113
john curl is offline john curl  United States
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It has been my interest to bring some of you up to date on how noise is generated in solid state components. I deliberately left out additional stages and 1/f, as well as popcorn noise, because they are relatively low in good quality parts at audio frequencies. RF, or test instrumentation, could be another matter entirely. Many of the contributions and references have been as good as I have seen anywhere. It is pointless to make a noisy circuit, if it can be avoided with a little knowledge of what is important. One thing that I often see is a relatively large resistor, (over 100 ohms) in series with many preamps. This can be good for RF control, but it can add significant noise to a phono stage, unnecessarily.
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Old 19th September 2003, 11:54 PM   #114
mikek is offline mikek
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Default Re: Re: Re: going by the book

Originally posted by Joe Berry

I hope you find the answers you are seeking.

Thanks Joe......i hope so too....something tells me you're somewhere in the south east...or west of England?
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Old 20th September 2003, 01:25 AM   #115
jam is offline jam  United States
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Location: Auburn, CA, USA

Thanks. Great stuff.

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Old 31st July 2004, 06:15 AM   #116
mikeks is offline mikeks  United Kingdom
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Originally posted by Fred Dieckmann
What happens if we run the bipolar transistor at 100ua, instead of 1 ma?

Low transconductance.... the sin that dare not speak its name.

What the heck would you run a BJT at 100uA for....??
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