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Compound amplifiers

N

Nemo

Jan 1, 1970
0
Can anyone recommend a good book or web resource where I could learn
about improving the bandwidth or noise performance of high gain op amp
circuits by using more complex configurations?

I've searched for terms like "compound amplifiers" but the examples I've
found show simply how to boost the output power of an op amp, which I'm
not interested in. I've also seen one or two circuits where people have
stuck JFET front ends on op amps, to get low Ein noise, but monolithic
op amp inputs are so good these days I suspect that is not the path to
follow any more.

I wondered about adding a gain block inside my feedback loop, so the
input op amp didn't have to have a gigantic GBW, but experiments along
those lines didn't seem to improve performance. So it looks like I need
a medium-to-advanced level text which will show me how to use novel and
obscure feedback topologies and what their tradeoffs are. Or perhaps
there are search terms I haven't thought of which would widen my
horizons a bit.

TIA,

Nemo
 
J

John S

Jan 1, 1970
0
I wonder, if you put all this into a little box, if anyone would buy
it.

An AC amplifier with a *lot* of paralleled BF862s in the front end
would be interesting, too. What's the square root of 16?

John

Err... 3^1.2618595

John S
 
J

John Devereux

Jan 1, 1970
0
Nemo said:
Can anyone recommend a good book or web resource where I could learn
about improving the bandwidth or noise performance of high gain op amp
circuits by using more complex configurations?

I've searched for terms like "compound amplifiers" but the examples I've
found show simply how to boost the output power of an op amp, which I'm
not interested in. I've also seen one or two circuits where people have
stuck JFET front ends on op amps, to get low Ein noise, but monolithic
op amp inputs are so good these days I suspect that is not the path to
follow any more.

I wondered about adding a gain block inside my feedback loop, so the
input op amp didn't have to have a gigantic GBW, but experiments along
those lines didn't seem to improve performance. So it looks like I need
a medium-to-advanced level text which will show me how to use novel and
obscure feedback topologies and what their tradeoffs are. Or perhaps
there are search terms I haven't thought of which would widen my
horizons a bit.

I was just today re-reading AN45 by the late great Jim Williams.

Rather poignant actually, as he describes late-night prototyping
sessions in between feeding his new-born baby.

Anyway the first two show low noise low drift composite amplifiers.

<http://cds.linear.com/docs/Application Note/an45.pdf>

Also AN21 "composite amplifiers"

<http://cds.linear.com/docs/Application Note/an21f.pdf>

Or just read the whole lot, see you in a few weeks :)

<http://www.linear.com/doclist/?tt=&ci=&dt=2&au=Jim+Williams&pn=&fd=&td=>
 
N

Nemo

Jan 1, 1970
0
Great leads, some meat to get my teeth into there. Phil's BF862 trick
sounds eminently do-able. I've got Jim Williams' article on vertical
amps, but the Tektonics Concepts book would never have occurred to me.
I've downloaded the LT app notes and am about to go through them. Thanks!

Nemo
 
M

Martin Riddle

Jan 1, 1970
0
John Devereux said:
I was just today re-reading AN45 by the late great Jim Williams.

Rather poignant actually, as he describes late-night prototyping
sessions in between feeding his new-born baby.

Anyway the first two show low noise low drift composite amplifiers.

<http://cds.linear.com/docs/Application Note/an45.pdf>

Also AN21 "composite amplifiers"

<http://cds.linear.com/docs/Application Note/an21f.pdf>

Or just read the whole lot, see you in a few weeks :)

<http://www.linear.com/doclist/?tt=&ci=&dt=2&au=Jim+Williams&pn=&fd=&td=>

Classic 3-bottle circuit ;)

Cheers
 
M

Martin Riddle

Jan 1, 1970
0
Jim Thompson said:
Can anyone recommend a good book or web resource where I could
learn
about improving the bandwidth or noise performance of high gain op
amp
circuits by using more complex configurations?

I've searched for terms like "compound amplifiers" but the
examples
I've
found show simply how to boost the output power of an op amp,
which
I'm
not interested in. I've also seen one or two circuits where people
have
stuck JFET front ends on op amps, to get low Ein noise, but
monolithic
op amp inputs are so good these days I suspect that is not the
path
to
follow any more.

I wondered about adding a gain block inside my feedback loop, so
the
input op amp didn't have to have a gigantic GBW, but experiments
along
those lines didn't seem to improve performance. So it looks like I
need
a medium-to-advanced level text which will show me how to use
novel
and
obscure feedback topologies and what their tradeoffs are. Or
perhaps
there are search terms I haven't thought of which would widen my
horizons a bit.

I was just today re-reading AN45 by the late great Jim Williams.

Rather poignant actually, as he describes late-night prototyping
sessions in between feeding his new-born baby.

Anyway the first two show low noise low drift composite amplifiers.

<http://cds.linear.com/docs/Application Note/an45.pdf>

Also AN21 "composite amplifiers"

<http://cds.linear.com/docs/Application Note/an21f.pdf>

Or just read the whole lot, see you in a few weeks :)

<http://www.linear.com/doclist/?tt=&ci=&dt=2&au=Jim+Williams&pn=&fd=&td=>



Classic 3-bottle circuit ;)

Cheers

I done two-bottles-of-Drambuie chip designs... one night, finished by
dawn ;-)

...Jim Thompson

[On the Road, in New York]

Just remembered that I have at least one paper on increasing
gain-bandwidth
product by using various compound OpAmp configurations.

It's not on a PC, it's on paper, so if you'd like a copy let me know,
and
sometime in September I'll scan it and send it out.

(I'm doing work at a secure installation, so must be on-site in NY :-(

...Jim Thompson

Still in NY? At least the weather isn't bad, but it is our monsoon
season.
There is supposed to be a great Greek restaurant in either Huntington or
Port jefferson, can't remember which.
Theres a long wait for a table.
Port Jefferson is nice in the summer, like Huntington lots of people
mulling around.

Cheers
 
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