THE "Universal" OP Amp

[John Fields]

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.

---
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The source is DC coupled and ground-referred, and since you're using
a single positive DC supply, the output is operating
emitter-follower class A and varies about a quiescent Vcc/2.

 

[Fred Bloggs]

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

The best course of action is for you to excuse yourself entirely from
USENET.

Instead of continually changing op amps, I am seeking to devise a
single design suited to a wide range of applications....

You never "devised" anything in your entire life and you're not likely
to. You might get a clue and ask yourself why there are so many
varieties of op amps in the first place. Even a mindless parrot would
answer that's because there are so many varieties of applications. So
your musings are plain stupidity.

The desired
criteria are as follows.

Who cares what you desire, get lost.

 

[Eeyore]

I no speaka Italian...but then this is not an Italian newsgroup.

Nor is it an English one.

Graham

 

[Trevor Morton]

Thank you John. I am sure this must be what I am looking for, but what
program do I import the list into to view the schematic?

Trevor _MORON_

 

[ehsjr]

Thank you John. I am sure this must be what I am looking for, but what
program do I import the list into to view the schematic?

SwitcherCAD free download from Linear:
http://www.linear.com/designtools/software/switchercad.jsp

Once you've got SWCAD, cut/paste Johns information to
Notepad and then save it with a .ASC extension. Then
open it with SWCAD

Ed

 

[Stanislaw Flatto]

...maybe class D is in order?

Ooopppsss, right, there was 'D' in his frequency specs!

Stanislaw

 

[Dirk Bruere at NeoPax]

Here we go again......

Well, let me tell you what I want.
A cheap amp that will pump a couple of amps at around 16V RMS from DC to
around 50HZ. Any onechip solutions?

--
Dirk

http://www.onetribe.me.uk - The UK's only occult talk show
Presented by Dirk Bruere and Marc Power on ResonanceFM 104.4
http://www.resonancefm.com

 

[Eeyore]

Well, let me tell you what I want.
A cheap amp that will pump a couple of amps at around 16V RMS from DC to
around 50HZ. Any onechip solutions?

16V rms = 44.8V pk-pk. Allow for device saturation of say 2V that would require
a supply of say 50V or +/- 25V.

A couple of amps > 32W in the load. Assuming efficiency of ~ 65% for a Class AB
amplifier that results in ~ 16W dissipation in the amplifier. Yes, that's
do-able in a single chip amplifier.

STM make a FET output one that'll do the job but I'm blowed if I can recall the
part number now. Probably a TDA something.
http://www.st.com/stonline/books/ascii/docs/1565.htm

Graham

 

[martin griffith]

Well, let me tell you what I want.
A cheap amp that will pump a couple of amps at around 16V RMS from DC to
around 50HZ. Any onechip solutions?

http://www.st.com/stonline/products/literature/ds/1461.pdf


martin