| Author |
Message |
Fred Bloggs
Guest
|
 Posted:
Sun Feb 06, 2005 9:21 pm Post subject:
Re: Lookinf for options for an Absolute Magnitude" or precis |
|
|
John Larkin wrote:
| Quote: | Crazy! It pulls the opamp input below ground, in violation of their
own abs-max ratings! That 2 volt p-p input must be on the very edge of
blowing the opamp up.
|
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...
|
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Fred Bloggs
Guest
|
| Posted:
Sun Feb 06, 2005 9:36 pm Post subject:
Re: Lookinf for options for an Absolute Magnitude" or precis |
|
|
Jim Thompson wrote:
| Quote: | What a crock! Relies on rail-to-rail OpAmp with negative rail of
first stage tied to ground :-(
|
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- |
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Glen Walpert
Guest
|
| Posted:
Sun Feb 06, 2005 10:08 pm Post subject:
Re: Lookinf for options for an Absolute Magnitude" or precis |
|
|
On Sat, 05 Feb 2005 23:17:09 GMT, "Clarence_A" <no@No.com> wrote:
| Quote: |
"John Larkin" <jjSNIPlarkin@highTHISlandPLEASEtechnology.XXX
wrote in message
news:tqia01pkmc4d8fbtavdrq12jd1sklq3qk5@4ax.com...
On Sat, 05 Feb 2005 22:09:31 GMT, "Clarence_A" <no@No.com
wrote:
"John Larkin" <jjSNIPlarkin@highTHISlandPLEASEtechnology.XXX
wrote in message
news:ltea015gvuthb414lq6kqc1kv806prgjef@4ax.com...
On Sat, 05 Feb 2005 19:01:17 GMT, "Clarence_A" <no@No.com
wrote:
Must work over substantial range, say .01 to .6 Volts RMS.
Serious responses only. Please.
I have a working circuit now, but there is some variation
between
positive and negative half cycles which seems to be
inherent.
Must be some easy way to eliminate this. Yes?
Can you post your circuit?
Sure, But it's easier to post a link!
http://www.analog.com/UploadedFiles/Data_Sheets/813995969OP191_29
1_491_c.pdf
On page seventeen!
Crazy! It pulls the opamp input below ground, in violation of
their
own abs-max ratings! That 2 volt p-p input must be on the very
edge of
blowing the opamp up.
So you see why I wanted a replacement!
|
Take a look at figure 2.42(d) in the classic 1966 Philbrich
Applications Manual for Computing Amplifiers at:
<http://www.analog.com/library/analogDialogue/archives/philbrick/computing_amplifiers.html>
it is in Part 2 discontinuities, but I recomment reading the entire
book esp the discussions of opamp error sources.
Glen
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Clarence_A
Guest
|
| Posted:
Sun Feb 06, 2005 10:35 pm Post subject:
Re: Lookinf for options for an Absolute Magnitude" or precis |
|
|
"Glen Walpert" wrote
| Quote: | "Clarence_A" wrote
"John Larkin" wrote
"Clarence_A" wrote
"John Larkin" wrote
"Clarence_A" wrote
Must work over substantial range, say .01 to .6 Volts
RMS.
Serious responses only. Please.
I have a working circuit now, but there is some variation
between
positive and negative half cycles which seems to be
inherent. Must be some easy way to eliminate this. Yes?
Can you post your circuit?
Sure, But it's easier to post a link!
http://www.analog.com/UploadedFiles/Data_Sheets/813995969OP191_291_491_c.pdf
On page seventeen!
Crazy! It pulls the opamp input below ground, in violation of
their own abs-max ratings! That 2 volt p-p input must be on
the very
edge of blowing the opamp up.
So you see why I wanted a replacement!
Take a look at figure 2.42(d) in the classic 1966 Philbrich
Applications Manual for Computing Amplifiers at:
http://www.analog.com/library/analogDialogue/archives/philbrick/c |
omputing_amplifiers.html>
| Quote: | it is in Part 2 discontinuities, but I recommend reading the
entire
book esp the discussions of opamp error sources.
Glen
|
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! |
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richard mullens
Guest
|
| Posted:
Mon Feb 07, 2005 12:05 am Post subject:
Re: Lookinf for options for an Absolute Magnitude" or precis |
|
|
Fred Bloggs wrote:
| Quote: |
John Larkin wrote:
Crazy! It pulls the opamp input below ground, in violation of their
own abs-max ratings! That 2 volt p-p input must be on the very edge of
blowing the opamp up.
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...
|
It seems that Clarence_A may unwittingly be Osama's secret weapon. |
|
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|
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Clarence_A
Guest
|
| Posted:
Mon Feb 07, 2005 12:46 am Post subject:
Re: Lookinf for options for an Absolute Magnitude" or precis |
|
|
"richard mullens" wrote
| Quote: | Fred Bloggs vomited:
John Larkin wrote:
Crazy! It pulls the opamp input below ground, in violation of
their
own abs-max ratings! That 2 volt p-p input must be on the
very edge of
blowing the opamp up.
|
Actually, none have failed. Just the performance is poor! With no
negative supply, there is no swing just clamping.
Fred's nonsense remarks here:
| Quote: | 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...
It seems that Clarence_A may unwittingly be Osama's secret
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! |
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|
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richard mullens
Guest
|
| Posted:
Mon Feb 07, 2005 1:27 am Post subject:
Re: Lookinf for options for an Absolute Magnitude" or precis |
|
|
Clarence_A wrote:
| Quote: | "richard mullens" wrote
Fred Bloggs vomited:
John Larkin wrote:
Crazy! It pulls the opamp input below ground, in violation of
their
own abs-max ratings! That 2 volt p-p input must be on the
very edge of
blowing the opamp up.
Actually, none have failed. Just the performance is poor! With no
negative supply, there is no swing just clamping.
Fred's nonsense remarks here:
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...
It seems that Clarence_A may unwittingly be Osama's secret
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. |
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John Larkin
Guest
|
| Posted:
Mon Feb 07, 2005 1:40 am Post subject:
Re: Lookinf for options for an Absolute Magnitude" or precis |
|
|
On Sun, 06 Feb 2005 16:35:14 GMT, "Clarence_A" <no@No.com> wrote:
| Quote: | 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."
|
Ha! Read the "ideas for design" clips in ED or EDN. Typically
nonsense.
John |
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John Larkin
Guest
|
| Posted:
Mon Feb 07, 2005 1:50 am Post subject:
Re: Lookinf for options for an Absolute Magnitude" or precis |
|
|
On Sun, 06 Feb 2005 15:21:42 GMT, Fred Bloggs <nospam@nospam.com>
wrote:
| Quote: |
John Larkin wrote:
Crazy! It pulls the opamp input below ground, in violation of their
own abs-max ratings! That 2 volt p-p input must be on the very edge of
blowing the opamp up.
In addition to knowing nothing about the 291, you can't read- the AM
Rating was obviously intent on saying GND+/-10V,
|
ABSOLUTE MAXIMUM RATINGS 1, 2
Supply Voltage . . . . . . . .. . . . . . . 16 V
Input Voltage . . . . . . . . . . . . . . . GND to VS 10 V
Is that what "GND to VS 10V" means? It looked like a misprint of "GND
to VS+10V" to me. I admit I didn't study the entire datasheet, this
being a newsgroup and I having real work to do of my own.
Why can't people proof datasheets?
| Quote: | Never mind- will not waste time on that individual...
|
Oh, please don't waste any of your valuable time on any of us.
John |
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Fred Bloggs
Guest
|
| Posted:
Mon Feb 07, 2005 1:53 am Post subject:
Re: Lookinf for options for an Absolute Magnitude" or precis |
|
|
Clarence_A wrote:
| Quote: |
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.
|
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.
| Quote: | 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!
|
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.
| Quote: | But Fred would have never found it, he isn't a working engineer, he's
on welfare!
|
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.
| Quote: |
[...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. |
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|
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John Larkin
Guest
|
| Posted:
Mon Feb 07, 2005 1:53 am Post subject:
Re: Lookinf for options for an Absolute Magnitude" or precis |
|
|
On Sun, 6 Feb 2005 08:12:52 +0000, John Woodgate
<jmw@jmwa.demon.contraspam.yuk> wrote:
| Quote: | Your roller clutches are equivalent to ratchet wheels, and diodes.
|
A good roller clutch is like a schottky diode, or almost an ideal
diode. They are amazing: no perceptable backlash or deadband, and very
little reverse leakage.
John |
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Fred Bloggs
Guest
|
| Posted:
Mon Feb 07, 2005 2:03 am Post subject:
Re: Lookinf for options for an Absolute Magnitude" or precis |
|
|
John Larkin wrote:
| Quote: | On Sun, 06 Feb 2005 15:21:42 GMT, Fred Bloggs <nospam@nospam.com
wrote:
John Larkin wrote:
Crazy! It pulls the opamp input below ground, in violation of their
own abs-max ratings! That 2 volt p-p input must be on the very edge of
blowing the opamp up.
In addition to knowing nothing about the 291, you can't read- the AM
Rating was obviously intent on saying GND+/-10V,
ABSOLUTE MAXIMUM RATINGS 1, 2
Supply Voltage . . . . . . . .. . . . . . . 16 V
Input Voltage . . . . . . . . . . . . . . . GND to VS 10 V
|
I already told you what they meant- try improving your reading
comprehension. |
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martin griffith
Guest
|
| Posted:
Mon Feb 07, 2005 2:06 am Post subject:
Re: Lookinf for options for an Absolute Magnitude" or precis |
|
|
On Sun, 6 Feb 2005 08:12:52 +0000, in sci.electronics.design John
Woodgate <jmw@jmwa.demon.contraspam.yuk> wrote:
| Quote: | I read in sci.electronics.design that John Larkin <jjSNIPlarkin@highTHIS
landPLEASEtechnology.XXX> wrote (in <f1ja01d165rcirkpdo1o77q4mr793v2iic@
4ax.com>) about 'Lookinf for options for an Absolute Magnitude" or
precision rectifier circuit.', on Sat, 5 Feb 2005:
On Sat, 5 Feb 2005 22:10:10 +0000, John Woodgate
jmw@jmwa.demon.contraspam.yuk> wrote:
I read in sci.electronics.design that John Larkin <jjSNIPlarkin@highTHIS
landPLEASEtechnology.XXX> wrote (in <ltea015gvuthb414lq6kqc1kv806prgjef@
4ax.com>) about 'Lookinf for options for an Absolute Magnitude" or
precision rectifier circuit.', on Sat, 5 Feb 2005:
snip
Unfortunately, the kid
wouldn't let me steal it to see in detail how it works. (;-)
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. |
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fuclarence
Guest
|
| Posted:
Mon Feb 07, 2005 2:17 am Post subject:
Re: Lookinf for options for an Absolute Magnitude" or precis |
|
|
Clarence_A wrote:
| Quote: |
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.
|
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.
| Quote: | 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!
|
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.
| Quote: | But Fred would have never found it, he isn't a working engineer, he's
on welfare!
|
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.
| Quote: |
[...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... |
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|
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Jim Thompson
Guest
|
| Posted:
Mon Feb 07, 2005 2:23 am Post subject:
Re: Lookinf for options for an Absolute Magnitude" or precis |
|
|
On Sun, 06 Feb 2005 20:17:48 GMT, fuclarence <xyz@xyz123456789.com>
wrote:
[snip]
| Quote: |
Why don't you plonk this and run- you little tutu wearing flake...
|
Sheeesh! What have we come to? Even Fred has to resort to an alias
to get read.
FuFred ;-)
...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. |
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