Discrete Opamp Open Design

[scott wurcer]

Originally Posted by jneutron

Why? Nothing to wear?

jn

Probabley makes me only three degrees from Jimmy Hoffa.

[lineup]

What is the latest of this OP Amp by Scott Wurcer. I find it hard to see the final word and a schematic.
If I understand Scott Wurcer he is playing at a league of his own. And this tend to make Op Amp not very basic or simple. But neverless it must be good. Because the man has been doing this to earn his daily bread.
Inform me please of a schematic showing the complete Op Amp so far.
Thank you

[scott wurcer]

Hi lineup, I posted a .pdf a couple of weeks ago with my current schematic and description of operation. I forgot the post number.

To me it's not that complicated and I think there are benefits to having the comp cap not referenced to either supply.

Another contender is a FET based JE990 with modern components, this makes sense since many of the ones out there are based on that and it would be nice to put a complete tested version out into the creative commons.

[bcarso]

Originally Posted by scott wurcer

To me it's not that complicated and I think there are benefits to having the comp cap not referenced to either supply.

I agree with both of the above. Quite a reasonable complement of parts for the purpose and the performance.

[kgrlee]

I suspect Guru Wurcer will Muntz loadsa stuff once he gets his hands dirty with the input stage of SW-OPA.

If I may make a teensy contribution .. You only need a single diode D1 on the i/p to avoid 'output reversal' on severe overload.

I'm using Cordell's 2n4401/3 models cos they give the worst results both for SW-OPA and my hacked FET990. Also, the real things will give 3.162Vp into 15R without bursting into flames .. at least for a short while

This newbie is really impressed with LTspice on this project. Only suspicious of the i/p stage. Even with fas42's improved BF862, there's stuff I don't believe but I have relatively little experience with FET i/p stages. Maybe try some much simpler circuits with the same i/p stage.

I also don't believe the Vbe on fas42, Cordell, Wurcer & Staccatiss' c2240/a970, BC546/556, n4401/3 BJT models compared to 1n4148/1n914

I'd like to replace a diode connected BJT with 1n4148 in my current mirror. If my (and Scott's) experience is kosher, this shouldn't be a problem as 1n4148 will just show a little more series R. But the models show more volts on the diode connected BJTs. Extra leakage & noise dun matter here.

[kf_tam]

Originally Posted by lineup

What is the latest of this OP Amp by Scott Wurcer. I find it hard to see the final word and a schematic.
If I understand Scott Wurcer he is playing at a league of his own. And this tend to make Op Amp not very basic or simple. But neverless it must be good. Because the man has been doing this to earn his daily bread.
Inform me please of a schematic showing the complete Op Amp so far.
Thank you

Hi Lineup,
Mr. Wurcer's latest is at #1568, with a slight mod to prevent latch up at #1776. The circuit discription is at #1675. In case you are wondering for a fully complementary frontend, that frontend is at #454, (though the symbols for P channel JFETs were wrong.)
Besides, he also published a FET input version of the JE990 discrete OPAMP at #1510

Regards,
Edward Tam

[kgrlee]

Originally Posted by kf_tam

.. with a slight mod to prevent latch up at #1776.

Du.uuh! Didn't see that. Guru Wurcer's mod does everything my pathetic contribution does .. & more

Gonna delete my post.

DAMN! Can't delete old posts! Forever shamed!

[scott wurcer]

Originally Posted by kf_tam

Hi Lineup,
Edward Tam

Thanks for keeping track, this weekend is a little busy but I hope to try the basic input stage by next weekend.

[scott wurcer]

Originally Posted by kgrlee

Du.uuh! Didn't see that. Guru Wurcer's mod does everything my pathetic contribution does .. & more

Gonna delete my post.

DAMN! Can't delete old posts! Forever shamed!

No worries mate!

[AndrewT]

post2045
R6 = 1m?
R18 = 1e6?