Lookinf for options for an Absolute Magnitude" or precision rectifier circuit.

Can we see that configuration?

(On custom I/C's I usually use multipliers to measure low-level RF.)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

In addition to knowing nothing about the 291, you can't read- the AM Rating was obviously intent on saying GND+/-10V, this design is not only ALL ABOUT input overdrive but also overdrive w/o phase inversion. There are 5K resistors in series with each input, diode clamps to V+ from there, and antiparallel diodes shunting the input PNP-NPN differential pairs. These resistors are designed to handle 5mA continuous current. The OP said:"Must work over substantial range, say .01 to .6 Volts RMS" and "but there is some variation between positive and negative half cycles" -DUHHUHHHH. Looks like Vout=Vbe-Vbc of the saturated Q33 pulldown- the Voh and Vol specs on Vce for the output transistors are something like 5mV at 50uA loading- but with loading to voltage below GND the pulldown saturation is inverted. Then 0.6RMS is something on the order of 1V peak negative, making for (1V-0.6)/10K=40uA max negative loading, so that a 100K pullup from the input follower output to Vs+ (=5V?) should keep the Q33 saturation from inversion and Vout~5mV or less during negative cycles- but the output follower will amplify this by x2 for +10mV output offset for the input negative half cycle- and this is comparable to the low end of the signal amplitude range. I suppose you could try something like this:

Never mind- will not waste time on that individual...

Heheh- the reference level about which rectification is performed is defined by the clamp level of the first amplifier buffer. Ok- make that "rectalication" for the alien fascist, Clarence-

Take a look at figure 2.42(d) in the classic 1966 Philbrich Applications Manual for Computing Amplifiers at:

it is in Part 2 discontinuities, but I recomment reading the entire book esp the discussions of opamp error sources.

Glen

One thing I failed to mention... you might want to AC-gain-up your signal before rectification... gets you out of offset problems, and can allow cheaper OpAmps.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

"Glen Walpert" wrote

RMS.

the very

entire

This is the kind of authoritative references I sought.

Background: I was contracted to do a design, so I was provided with the design of a previous unit they wanted to move into the new application.

For various reasons I simply started to design a new circuit block by block (as I modeled the damn thing) finding many problems with the previous design as I progressed.

Since I need to change what the "app note paste artist" put together, I need to refute his premise that "it wouldn't be published if it wasn't correct."

I was prepared to do so, however more ammunition is always a good strategy when dealing with 'entrenched' management.

Jim, Win, and Philbric, (TNX Glen) should be an army of expert opinion to break down the walls!

Besides lives are at stake (Not just the job!) these units go on commercial aircraft! Scary!

It seems that Clarence_A may unwittingly be Osama's secret weapon.

"richard mullens" wrote

their

very edge of

Actually, none have failed. Just the performance is poor! With no negative supply, there is no swing just clamping.

Fred's nonsense remarks here:

the AM

is not only

inversion. There

from

differential

current.

Volts RMS"

half

Q33

transistors are

voltage below

something on the

negative

to Vs+

Vout~5mV or

amplify this

cycle- and

range. I

weapon.

Fred ignores the fact that I found the problem, and will fix it. It was NOT MY DESIGN, it is an Application note with an (horror) error. As if we haven't all found those. I only ask for verification, since anyone who thinks they are always right, or are perfect aren't!

But Fred would have never found it, he isn't a working engineer, he's on welfare!

This is his usual mud slinging and an attempt to pull down everything to his level. I PLONKED him long ago and do not miss his foul mouth and poor manners!

We all have points of view here. I'm not certain that one can say that any one's person's view is any more legitimate than an other's. In the end, it all comes down to evidence or in some cases the lack of it !

Anyway, I'm sure that you must appreciate the joy I felt when that idea came into my head.

There is no "horror" error in that circuit- it is very well- designed and a solid product. It is less than 1% error for the specified signal level. You are an incompetent p.o.s. and you can't "fix" anything. It was immediately clear to me how to do this- but it will a cold day in hell before I tell you.

Anyone who thinks he/she/it can just hack any old rectifier ckt to work at "10mVRMS", single supply or not, and not encounter problems is a ***MORON***.***MORONS*** EVERYWHERE *ALWAYS* LACK SENSE OF SCALE.

I take that as a compliment seeing as how you just slandered AD app dept- a group that wouldn't consider the likes of you to do so much as empty the garbage cans.

*ANYONE* who subcontracts anything to you should be fired- must be a mindless application of the low-bidder mentality-or maybe an ethnic quota thing to look at your pathetic broken English- whatever, they will regret it. [...snip moronic bs...]

You should drop dead- I'm sure there is a consensus on that.

You're typical of what I've encountered on USENET- a second rate little blowhard of nearly zero intelligence and/or worth- a very dull uninteresting person devoid of know-how.

I already told you what they meant- try improving your reading comprehension.

There is no "horror" error in that circuit- it is very well- designed and a solid product. It is less than 1% error for the specified signal level. You are an incompetent p.o.s. and you can't "fix" anything. It is immediately clear to me how to do this- but it will be a cold day in hell before I tell you.

Anyone who thinks he/she/it can just hack any old rectifier ckt to work at "10mVRMS", single supply or not, and not encounter problems is a ***MORON***.***MORONS*** EVERYWHERE *ALWAYS* LACK SENSE OF SCALE.

I take that as a compliment seeing as how you just slandered AD app dept- a group that wouldn't consider the likes of you to do so much as empty the garbage cans.

*ANYONE* who subcontracts anything to you should be fired- must be a mindless application of the low-bidder mentality-or maybe an ethnic quota thing to look at your pathetic broken English- whatever, they will regret it. [...snip moronic bs...]

You should drop dead- I'm sure there is a consensus on that.

You're typical of what I've encountered on USENET- a second rate little blowhard of nearly zero intelligence and/or worth- a very dull uninteresting person devoid of know-how.

Why don't you plonk this and run- you little tutu wearing flake...

I read in sci.electronics.design that martin griffith wrote (in ) about 'Lookinf for options for an Absolute Magnitude" or precision rectifier circuit.', on Sun, 6 Feb 2005:

I said I DIDN'T steal it. Maybe YOU should go into politics or religion.(;-)

--
Regards, John Woodgate, OOO - Own Opinions Only. 
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

I plonked Mullens ages ago. Didn't you notice the "ntlworld"... he's another Bemelman-style cretin.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

John Larkin wrote: > On Sun, 06 Feb 2005 15:21:42 GMT, Fred Bloggs > wrote: >

I see now that we were crediting the fascist with far too much observational ability- all he was doing was SPICE simulation, and the AD model does not begin to model input overdrive accurately- producing phase reversal at ridiculously low overdrive. So the idiot hasn't even gotten to square one- what a pathetic little loser- all he was doing was looking a signal shapes and noticed a sine thingie where output should be flat lined- my, my, my, what a stickler for detail he is! Why is it all you Nazi types are so damned stupid....

snip

tut,tut, stealing from little children, maybe you should go into politics or religion

martin

Serious error. All shortcuts have disappeared. Screen. Mind. Both are blank.

You mean it "ISN'T" a joke? (:>)

say that any one's person's view is any more legitimate than an other's. In the end, it all comes down to evidence or in some cases the lack of it !

Strange statement. Fred never has anything constructive to say to me, or about me if he can fine someone to reply, since I never see his postings!

Do you not see the difference between constructive comment and deliberate nonsense? Remember that Fred Bloggs has nothing at stake! I am the only one doing the design work on the electronics of a critical piece of aircraft safety equipment. The design I was told to "Modify, is ON aircraft now! Scares me, and I wasn't the one who did the deed!

that idea came into my head.

I am sure that the feeling was accompanied by the realization that it meant you were still alive? Congratulations, that is certainly something to celebrate.

Have a good day.

flake...

alias

Gee, was that Freddy?

It did look like him! Or it rather sounded like him. He hasn't changed at all.

I will be talking to the AD Engineer responsible for the product on Monday to advise him and find if there is another explanation for the problem. He wasn't in on Friday.

I do not work in a vacuum, and communicate with the responsible parties at all venders I use.

By the way, many of the product people know me. We have a beer at the various shows. (I know, Wine would be better.)