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Having some feedback to the output is a win, because the feedback goes both ways--the op amp can provide some of the output. It's also a bit quicker for large signal stuff, because the error current goes straight out the supply leads without going through the frequency compensation stuff in the front end. Of course that complicates the overall frequency compensation of the amp.
Making composite amps with decent settling behaviour can be pretty tough.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 email: hobbs (atsign) electrooptical (period) net http://electrooptical.net
Can we please declare a weekend moratorium on pissing contests? Pretty please?
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 email: hobbs (atsign) electrooptical (period) net http://electrooptical.net
-- Works for me! :-)
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sI thinking you are confusing your app with peaking coils which were one of several techniques used to broadband the amplifier- that's a totally different application and it was practical because the reactance was only important in the 10's KHz band or higher- this is not the case for a 20-20K Hz headphone circuit.
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The base resistance is like 1 ohm? That doesn't seem like enough to explain the difference I see.
The power supply noise is in the 1 to 3 nV/rtHz range. (There are three bipolar supplies.)
Opamps are pretty amazing these days. FET inputs with 8nV and a few pF, 10uV Vos bipolar's with 3nV.. (I've only looked a little at the
1nV bipolar's) With the exception of the OPA124* they've always met spec noise wise.No worries, I'm mostly just curious why my negative supplies are a bit less noisy. It could be my negative supply is quiteter(sp) to begin with. (I think I measured that though)
George H.
*The opa124 has a big peak in voltage noise out beyond.. 50 kHz? I'd have to check my notes. If you stay below that it may meet it's 6nV spec. (I never bothered measureing.)
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y mYeah it seems like you can get gob's of current out of it. You're not stuck with what the opamp can supply. There might be issues near zero. So I think you're suggesting included John's R6 and taking the feedback from after that. (At least that's how I drew it.)
Well if it was easy I would have already heard about it.
George H.
t- Hide quoted text -
You're a newsgroup abuser, not a man.
Write to your congresswoman.
John
Bullshit. That is what YOU would have liked them to have said.
Essentially, you have proven nothing except that fact that you do NOT know what ANY others think.
Obviously not, idiot. You are 100% convoluted, none-the-less.
Actually, me pegging you as an idiot is far more accurate than you pegging all the members of the group (and then some) as thinking one way or the other about a given topic. You are about as clueless as any man can get.
I can guarantee you that Larkin is the only asshole in the group that cannot comply.
For one thing, that is NOT what JF is doing.
Larking would like to think that he could win a pissing contest, but he falls short of the requisite needs of being a man, and having a dick.
The closest he comes to having a dick is the fact that he is typically a d*****ad.
Dream on. If you had any credibility I'd find the thread, but since it's you, why should I bother?
I haven't bothered to prove anything. I've just made an assertion. It happens to be a correct assertion, but you are too dim to realise this, and too low in the pecking order for your opinion to matter.
Do go on. This group in short on good jokes, and you make a pretty good substitute.
-- Bill Sloman, Nijmegen
Sorry cast boy, but if we are declaring levels of attainment and awareness here, you would certainly be the loser against me.
You don't even know what a 555 timer IC is for, much less the fact that it is still used. Far more than you are willing to believe, since it proves you wrong.
And you are... both wrong AND the loser. Bye.
Am not!
ftp://jjlarkin.lmi.net/Chokes.JPG
John
Hilarious. And very unclear on the concept.
John
The ADA4898 doesn't have a big noise peak. And all that about PNPs (e.g. the 2N4250) is done to death in Motchenbacher. It's good stuff, but as far as currently available components go, it's out of date. Good NPNs are now generally better than good PNPs, and have been for a while.
There's been a big outpouring of great +-15V op amps in the past three years or so. I never thought I'd see it, but there it is.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 email: hobbs (atsign) electrooptical (period) net http://electrooptical.net
What is the book?
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e d dI thinking you're missing context there: the tube people enjoyed the benefit of hundreds of volts of power supply to play with, and there was no necessity to consider physical size and power consumption. I seriously doubt the 30H choke has small enough resistance to make its quiescent DC voltage drop insignificant, which reduces your available signal swing for the load. Although interesting from a historical perspective, those circuits just aren't feasible here.
Unlikely in that case, so what else is there, other than cap leakage noise, resistive noise or measurement uncertainty ?. I think you posted a circuit, but don't have it to hand now. One thing we found is that you need to run the rig from well decoupled batteries and enclose everything in a die cast or other screened box with bnc for measurement o/p if you are trying to take measurements at very low level. Ambient noise swamps everything otherwise....
Some of the ad devices are very good with regard to offset voltages and not expensive either. Am using ad8574 quads for a back burner project and the specs are amazing in comparison to some of the older devices.
As Phil mentioned, am probably completely out of date w/regard to audio, but it has been 30+ years. The 709 and 741 class devices we were using at the time needed all kind of hacks, such as bleed resistors to one of the rails to get rid of the crossover distortion and other response tweaks. Different world out there now...
Regards,
Chris
Ghirardi, Radio Physics Course, 1932. I have a heap of old electronics books, going back to 1921. People *did* use a lot of transformers and inductors in signal paths, as the RF boys still do. Gain-bandwidth used to be expensive.
John
Dream on.
I know what Hans Camenzind claims that he though he was designing it to do, and I've seen lots of exampled of the ways in which it is used. I'm well aware that it still sells in large number, for use in legacy designs, and that "legacy designers" still design it into new circuits, because it is easier and quicker to adapt an old circuit than to redesign around mre modern parts.
None of this falsifies the point I make - that the 555 stopped being a widely applicable circuit back around 1980.
Since you half-baqked arguments don't address this particualr point, they don't "prove me wrong". They do prove that you can't think straight, which makes you=A0 "both wrong AND the loser. =A0Bye."
-- Bill Sloman, Nijmegen
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