J
Jim Thompson
Guest
On Mon, 28 May 2018 15:26:58 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
I have a paper somewhere that discusses GBW-product and optimization
of the two-OpAmp composite. Quite nicely done, as I recall...
unfortunately I haven't re-found it :-(
...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| STV, Queen Creek, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
Thinking outside the box... producing elegant solutions,
by understanding what nature is hiding.
"It is not in doing what you like, but in liking what you do that
is the secret of happiness." -James Barrie
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 05/28/18 14:56, Jim Thompson wrote:
On Sun, 27 May 2018 15:09:33 -0400, Phil Hobbs
pcdhSpamMeSenseless@electrooptical.net> wrote:
Hi, all,
I'm generally prejudiced against composite amplifiers (two op amps
inside one feedback loop) because they're generally squirrelly, with
poor settling performance and weird transient response.
On the other hand, my aversion to them means that I don't have as much
experience with them as do composite-amp fans. So what do you folks say
about them?
Orchids? Onions? Actual expertise?
Cheers
Phil Hobbs
I don't have time (*) to join the discussion, but read this...
http://www.analog-innovations.com/SED/CompositeAmplifiers.pdf
I have that one, thanks. Lots of the circuits are summing-junction
snoopers, i.e. circuits wih a slow-but-accurate amp looking at the
time-averaged input error of a fast-but-cruder amp, and nulling it out.
That's a useful trick sometimes, and are examples of "putting a bandaid
on the fast circuit", which I was talking about upthread.
There are other sorts of bandaids, e.g. the White cathode follower and
many sorts of local feedback. Often the key is to figure out a way that
the bandaid can be much slower than the main amplifier, as in the
snooper circuits.
I often use op amps to force JFETs to run at exactly I_DSS, for
instance--the problem then is to keep the low-frequency noise from going
nuts.
Cheers
Phil Hobbs
I have a paper somewhere that discusses GBW-product and optimization
of the two-OpAmp composite. Quite nicely done, as I recall...
unfortunately I haven't re-found it :-(
...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| STV, Queen Creek, AZ 85142 Skype: skypeanalog | |
| Voice480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
Thinking outside the box... producing elegant solutions,
by understanding what nature is hiding.
"It is not in doing what you like, but in liking what you do that
is the secret of happiness." -James Barrie