Standard non-inverting opamp with a cap across + and - terminals...... Why?

an

special.

But what could be cheaper? One more resistor and one lil' capacitor. Or roughly 3-4 Cents in quantities.

Yeah. In the good old days when opamps came in TO cans all this noise shielding was a lot easier. And in the tube days there simply were no noise issues :-)

matching

an

special.

In my opinion, there's a better place to put your 3-4¢, as in...

...Jim Thompson

drive

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Bode

an

special.

Ahm, what's the difference to the proposed solution?

drive

matching

terminal.

Bode

resenting an

special.

The ADI kid was doing an RC +Input to -Input... my approach is as old as the hills... feed-forward.

ADI kiddie's method adds a pole AND a zero (the R).

Analyze it... pencil and paper... if you can manage ;-)

...Jim Thompson

drive

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terminal.

Bode

resenting an

special.

I meant the last image in the AD link. It's the same thing ... and yeah, it's age old.

drive

signals

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terminal.

Bode

resenting an

and

special.

I didn't get down that far :-) Compensation +Input to -Input is _not_ adequate for anything other than EMI inducements.

...Jim Thompson

Yep, that's the only reason I ever use it. And even then only if the client calls me too late, the layout is done and the delivery date is like "should have been last month".

grounded.

That's what weasels do.

I think they are unused, one in the original box. Flea market finds.

John

grounded.

Oh. Right. Good point.

John

Sure, it's easy if you want to add three more parts. I need a lot of super-stiff sources, so my ideal solution is a simple opamp follower with a big ceramic cap to ground.

Some opamps put the internal rolloff capacitor deep inside the amp, so the external cap adds another pole and makes things ring or oscillate. But some amps hang one end of their rolloff cap on the output pin; in that case, adding an external cap decreases that rolloff frequency but doesn't add another pole, so it remains stable with large cap loading. The LM8261 "C-load opamp" does this by design, but it's expensive. I think some opamps, like the MC33503, do this by accident and are cheaper. I'll try some.

John

And the French. Sloman lives close enough that it seems to have rubbed off.

How can they tell they are on strike, in a nation where they generally do nothing?

It looks like the only functional Eiffel Tower is outside of France these days.

Oh. Right. Good point.

John

Your flea markets must be a lot more interesting than ours. Here you can find old riding boots, tractor glow plugs or skillets. No tech marvels.

When was the last time you visited Dayton, Ohio in roughly the middle of May, Joerg? :-)

May,

Hey that's a good idea..

someone want to organize a SED meet at Dayton?

Mark

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grounded.

No. I'm clarifying what I said earlier, and filling detail.

Obviously, what I should have said is that only a proportion of the sub-26mV signal gets rectified, and that proportion decreases as the signal declines below 26mV, but it's hard enough to get you guys to read short declarative sentences without raising the level of difficulty with qualiflying clauses.

Your own responses have been getting progressively more intellectual content as the discussion goes on, and to that extent you too are "weaseling".

-- Bill Sloman, Nijmegen

has

circuit

grounded.

As long as you quit repeating the "26 mV" nonsense, I've done a service to humanity. RF power meters and crystal radios can continue to work without fear of your disapproval.

John

The last time I was at a hamfest was some time way back in the last century :-)