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THE "Universal" OP Amp

T

Trevor Morton

Jan 1, 1970
0
Well, I've seem to have managed to confound another group. So, please
excuse me for importing this thead.

Instead of continually changing op amps, I am seeking to devise a
single design suited to a wide range of applications. The desired
criteria are as follows.

4-12V power supply
Bandwidth _DC_ through 20KHz
DC coupled in and out
Unity to 20 gain, variable by trimpot
Low power DIP package
Drive resistive load of 20 to 200 ohms,
Output up to 2A, with Darlington follower
Swing as close to rail as is practical

At first, I thought such specs might be mutually exclusive in a fixed
design. However, if there are such limitations, they seem to be
receeding fast.

For example, there is the "new" OPA569, rated at 2A. It meets my
requirements except only operates up to 5.5V.

http://focus.ti.com/docs/prod/folders/print/opa569.html

Can someone explain, in theory or practice, why something like what I
am looking for cannot (apparently) be achieved with a "standard" op
amp and a couple of transistors? I am aware there are plenty such
devices dediciated strictly to audio, but they do not fit the bill on
several counts.

I can imagine this would be of lasting value to thoses who lack the
full range of engineering skills.

Thank you for any input.

Trevor Morton
 
R

Robert Baer

Jan 1, 1970
0
Trevor said:
Well, I've seem to have managed to confound another group. So, please
excuse me for importing this thead.

Instead of continually changing op amps, I am seeking to devise a
single design suited to a wide range of applications. The desired
criteria are as follows.

4-12V power supply
Bandwidth _DC_ through 20KHz
DC coupled in and out
Unity to 20 gain, variable by trimpot
Low power DIP package
Drive resistive load of 20 to 200 ohms,
Output up to 2A, with Darlington follower
Swing as close to rail as is practical

At first, I thought such specs might be mutually exclusive in a fixed
design. However, if there are such limitations, they seem to be
receeding fast.

For example, there is the "new" OPA569, rated at 2A. It meets my
requirements except only operates up to 5.5V.

http://focus.ti.com/docs/prod/folders/print/opa569.html

Can someone explain, in theory or practice, why something like what I
am looking for cannot (apparently) be achieved with a "standard" op
amp and a couple of transistors? I am aware there are plenty such
devices dediciated strictly to audio, but they do not fit the bill on
several counts.

I can imagine this would be of lasting value to thoses who lack the
full range of engineering skills.

Thank you for any input.

Trevor Morton
Well, find an opamp that you like and will do everything except the
drive. Then add the equivalent to the LH0002 (damn! been obsoleted) as a
current buffer, giving a composite opamp with good drive capability.
If you choose properly, the opamp can go to +/-18V supply (or 0/36V).
 
S

Stanislaw Flatto

Jan 1, 1970
0
Trevor said:
Well, I've seem to have managed to confound another group. So, please
excuse me for importing this thead.

Instead of continually changing op amps, I am seeking to devise a
single design suited to a wide range of applications. The desired
criteria are as follows.

4-12V power supply
Bandwidth _DC_ through 20KHz
DC coupled in and out
Unity to 20 gain, variable by trimpot
Low power DIP package
Drive resistive load of 20 to 200 ohms,
Output up to 2A, with Darlington follower
Swing as close to rail as is practical

At first, I thought such specs might be mutually exclusive in a fixed
design. However, if there are such limitations, they seem to be
receeding fast.

For example, there is the "new" OPA569, rated at 2A. It meets my
requirements except only operates up to 5.5V.

http://focus.ti.com/docs/prod/folders/print/opa569.html

Can someone explain, in theory or practice, why something like what I
am looking for cannot (apparently) be achieved with a "standard" op
amp and a couple of transistors? I am aware there are plenty such
devices dediciated strictly to audio, but they do not fit the bill on
several counts.

I can imagine this would be of lasting value to thoses who lack the
full range of engineering skills.

Thank you for any input.

Trevor Morton
Your "Universal" is false. It is a solution to your requirements,
nothing "Universal" about it. So sit again on the specs of this circuit
and watch out on conflictic definitions e.g. 12 volt/20ohm load/ low
power package.
----> 144/20 = ~7W so where is the low power?

HTH

Stanislaw
 
E

Eeyore

Jan 1, 1970
0
Trevor said:
Well, I've seem to have managed to confound another group. So, please
excuse me for importing this thead.

Instead of continually changing op amps, I am seeking to devise a
single design suited to a wide range of applications. The desired
criteria are as follows.

As I've explained elsewhere, what you want is an *AMPLIFIER*. Your 'spec' is
*NOT* an op-amp. An op-amp is typified for example by gain that's as high as
possible typically 100,000 or greater at DC.

When you get to understand the difference, the penny may finally drop.


Graham
 
P

Phil Allison

Jan 1, 1970
0
"Trevor Moron"
Well, I've seem to have managed to confound another group. So, please
excuse me for importing this thead.



** The only thing "confounded" is you - Moron.

Can't even get the simplest LM386 circuit to work.





........ Phil
 
G

Genome

Jan 1, 1970
0
Trevor Morton said:
Well, I've seem to have managed to confound another group. So, please
excuse me for importing this thead.

Instead of continually changing op amps, I am seeking to devise a
single design suited to a wide range of applications. The desired
criteria are as follows.

4-12V power supply
Bandwidth _DC_ through 20KHz
DC coupled in and out
Unity to 20 gain, variable by trimpot
Low power DIP package
Drive resistive load of 20 to 200 ohms,
Output up to 2A, with Darlington follower
Swing as close to rail as is practical

At first, I thought such specs might be mutually exclusive in a fixed
design. However, if there are such limitations, they seem to be
receeding fast.

For example, there is the "new" OPA569, rated at 2A. It meets my
requirements except only operates up to 5.5V.

http://focus.ti.com/docs/prod/folders/print/opa569.html

Can someone explain, in theory or practice, why something like what I
am looking for cannot (apparently) be achieved with a "standard" op
amp and a couple of transistors? I am aware there are plenty such
devices dediciated strictly to audio, but they do not fit the bill on
several counts.

I can imagine this would be of lasting value to thoses who lack the
full range of engineering skills.

Thank you for any input.

Trevor Morton

Doesn't sound too universal to me..... Sounds like an amplifier that that
needs desired criteria of......
4-12V power supply
Bandwidth _DC_ through 20KHz
DC coupled in and out
Unity to 20 gain, variable by trimpot
Low power DIP package
Drive resistive load of 20 to 200 ohms,
Output up to 2A, with Darlington follower
Swing as close to rail as is practical

..................

I can imagine this would be of lasting value to thoses who lack the
full range of engineering skills.

Apart from those who want a 'Universal Op-Amp' that does something
different.
Well, I've seem to have managed to confound another group. So, please
excuse me for importing this thead.

That's OK....... (If you want to come across as a pretentious ****) Eeeyore
will be along soon to not give you the design you thought you wanted in the
first place........

After someone else has told him how to do it and then he won't anyway.

I think that's how it works.

Bonza!

DNA
 
E

Eeyore

Jan 1, 1970
0
Genome said:
That's OK....... (If you want to come across as a pretentious ****) Eeeyore
will be along soon to not give you the design you thought you wanted in the
first place........

My recommendation was a car audio amplifier chip.

However the OP steadfastly refuses to usefully elaborate about his application.

Graham
 
P

Phil Allison

Jan 1, 1970
0
"EeysoreFuckwit "
My recommendation was a car audio amplifier chip.


** Will never work satisfactorily with a 4 volt supply.

However the OP steadfastly refuses to usefully elaborate about his
application.


** That is because he is a fucking TROLL and does not have one.




....... Phil
 
G

Genome

Jan 1, 1970
0
Eeyore said:
My recommendation was a car audio amplifier chip.

However the OP steadfastly refuses to usefully elaborate about his
application.

Graham

Here we go again......

DNA
 
P

Phil Allison

Jan 1, 1970
0
"Trevor Moron"
Well, I've seem to have managed to confound another group. So, please
excuse me for importing this thead.


** How come you made no reply to this post ???

--------------------------------------------------

"Trevor Morton"
I thought the LM386 was an audio amp (not to DC), but had a try anyway
with a 5Hz squarewave. Distortion was pretty bad. Also, regardless of
frequency, I only get 1V swing out with 6V in. It is supposed to have
a built-in gain of 20. This I don't understand.

** Try again - you got it fouled up somehow.

With a 4 volt supply, square wave drive and 33 ohm load ( no coupling cap),
the output is a clean. 2.6 volt p-p square wave at *any* frequency up to
20kHz.

With a 12 volt supply, same set up as above, the output swing is 10 volt
p-p.

Same p-p swings apply to a sine wave input as well.
BTW

Make sure your input signal does not have a DC offset.

........ Phil

---------
----------------------------------------

** Cat got your tongue - fuckwit ?

Meeeeoooowww



......... Phil
 
J

Jamie

Jan 1, 1970
0
Robert said:
Well, find an opamp that you like and will do everything except the
drive. Then add the equivalent to the LH0002 (damn! been obsoleted) as a
current buffer, giving a composite opamp with good drive capability.
If you choose properly, the opamp can go to +/-18V supply (or 0/36V).
Really, i just received 50 LH0002 to replace a few bad one's in some old
FENNER/CONTRX units. i think we paid around 2 bucks each.
 
J

John Popelish

Jan 1, 1970
0
Trevor said:
Well, I've seem to have managed to confound another group. So, please
excuse me for importing this thead.

Instead of continually changing op amps, I am seeking to devise a
single design suited to a wide range of applications. The desired
criteria are as follows.

4-12V power supply
Bandwidth _DC_ through 20KHz
DC coupled in and out
Unity to 20 gain, variable by trimpot

I think you can combine the closed loop bandwidth with the
maximum gain and say that the opamp must have an open loop
gain bandwidth product of at least 20*20k=400kHz. A little
extra might not hurt. Lots of opamps have about a 5. to
1MHz GBW product.
Low power DIP package
Drive resistive load of 20 to 200 ohms,
Output up to 2A, with Darlington follower
Swing as close to rail as is practical
(snip)

How about 2 in an 8 pin DIP?
Take a look at the LMC6482
http://cache.national.com/ds/LM/LMC6482.pdf
supply range 3 to 15 volts, rail-to-rail input and output,
GBW=1.5 MHz (1 MHz with 3 volt supply).

Add a complementary emitter follower made of high gain
transistors like ZTX698B and ZTX788A
http://www.zetex.com/3.0/pdf/ZTX688B.pdf
http://www.zetex.com/3.0/pdf/ZTX788A.pdf

And get a peak output current greater than 1 amp something
like within a volt or so from each rail (more if you allow 2
volts from rails).

You will have cross over distortion, but you didn't spec that.

For applications that don't need the high output current,
eliminate the followers.
 
M

mpm

Jan 1, 1970
0
I am seeking to devise a single [op amp] design suited to a wide range
of applications...

You ever notice that when all you see are hammers, everything looks
like a nail?

-mpm
 
M

Michael A. Terrell

Jan 1, 1970
0
Jamie said:
Really, I just received 50 LH0002 to replace a few bad ones in some old
FENNER/CONTRX units. I think we paid around 2 bucks each.


That doesn't mean that they are not obsolete. I still have some NOS
RTL and DTL ICs, but that doesn't mean that you could buy production
quantities. Even Jameco is clearing out their remaining LH0002CN ICs.


--
Service to my country? Been there, Done that, and I've got my DD214 to
prove it.
Member of DAV #85.

Michael A. Terrell
Central Florida
 
B

Ban

Jan 1, 1970
0
Trevor said:
Well, I've seem to have managed to confound another group. So, please
excuse me for importing this thead.
To me it demonstrates only your disability to understand how an opamp
functions.

Instead of continually changing op amps, I am seeking to devise a
single design suited to a wide range of applications. The desired
criteria are as follows.

4-12V power supply
Bandwidth _DC_ through 20KHz

single supply
GBW
DC coupled in and out

every opamp
Unity to 20 gain, variable by trimpot

unity gain stable, but I want infinite gain
ridiculous- trimpot
Low power DIP package

somewhat outdated these days. Only for hobbyists
Drive resistive load of 20 to 200 ohms,
Output up to 2A, with Darlington follower

I rather would like to be able to drive complex loads too.
12V/20R= 600mA to me, not 2A. What about MOSFET output stage?
Swing as close to rail as is practical
Rail to Rail output
At first, I thought such specs might be mutually exclusive in a fixed
design. However, if there are such limitations, they seem to be
receeding fast.
You left out some very important data like PSRR, CMRR, common mode voltage
range, input impedance, offset voltage, Bias current, noise, distortion,
linearity, overload recovery etc.
For example, there is the "new" OPA569, rated at 2A. It meets my
requirements except only operates up to 5.5V.

2A with only 150mV voltage drop. Can't be a darlington stage.
Something like an LM386 already exists for eons.
http://focus.ti.com/docs/prod/folders/print/opa569.html

Can someone explain, in theory or practice, why something like what I
am looking for cannot (apparently) be achieved with a "standard" op
amp and a couple of transistors? I am aware there are plenty such
devices dediciated strictly to audio, but they do not fit the bill on
several counts.

I can imagine this would be of lasting value to thoses who lack the
full range of engineering skills.

The industry doesn't produce parts for beginners like you only. Better you
start understanding at least the most fundamental ideas behind opamps. Even
a 741 is far more versatile than your data. You seem to have only audio and
LED drivers in mind.
Thank you for any input.

I would say GIGO, my answer included. :-(
Trevor Morton

Moron would be appropriate. There is s.e.b. for posts like this, where
stupid questions do not exist.
 
R

Robert Baer

Jan 1, 1970
0
Stanislaw said:
Your "Universal" is false. It is a solution to your requirements,
nothing "Universal" about it. So sit again on the specs of this circuit
and watch out on conflictic definitions e.g. 12 volt/20ohm load/ low
power package.
----> 144/20 = ~7W so where is the low power?

HTH

Stanislaw
....maybe class D is in order?
 
R

Robert Baer

Jan 1, 1970
0
Jamie said:
Really, i just received 50 LH0002 to replace a few bad one's in some old
FENNER/CONTRX units. i think we paid around 2 bucks each.
DigiKey thinks it is obsolete.
 
F

Fred Bloggs

Jan 1, 1970
0
Ban said:
To me it demonstrates only your disability to understand how an opamp
functions.

Not nearly as pronounced as your *inability* to write in
English-approaching a *disability* for sure.
 
B

Ban

Jan 1, 1970
0
Fred said:
Not nearly as pronounced as your *inability* to write in
English-approaching a *disability* for sure.

what about your Italian?
I would say GIGO, my answer included.
So don't take it too serious Fred.
 
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