Discrete Opamp Open Design

[homemodder]

Four of those already dont qualify, over 8 transistors.

No CFB types ???

[dirkwright]

Originally Posted by homemodder

Four of those already dont qualify, over 8 transistors.

No CFB types ???

current sources are not counted. But, even so, if you like it and it has more than 8, then since you're a genius you can fix it, right?

I saw some CFB types, but they had way more than 8 transistors. Do you have any examples you'd like to share or are you just going to talk talk talk???

[john curl]

Anything less complex than a Jensen 990 is a joke, and not worthy of consideration. We are looking for EXCELLENT circuits that we would use in the best audio equipment available today.

[hitsware]

> Anything less complex than a Jensen 990 is a joke

That's the strangest statement .........

[dirkwright]

Originally Posted by john curl

Anything less complex than a Jensen 990 is a joke, and not worthy of consideration. We are looking for EXCELLENT circuits that we would use in the best audio equipment available today.

I thought you already did that? You're asking US to design something for you?

That would be like Luke Skywalker teaching Yoda how to use The Force.

[hitsware]

Originally Posted by abraxalito

Digikey is listing both the J76 and K213 series as obsolete. So that looks like a dead end then.

Toshiba has some high-gm FETs (even better on paper than Renesas) but they're rather low voltage and have higher thresholds than the laterals. Along with negative Vgs threshold temp coeff.

Hitachi FET To-220ab 200v .5A 30W GSD *SS | HITACHI *SS | Distributed By MCM
Hitachi Hitachi FET To-220ab N-ch 15V .5A 30W GDS *SS | 2SK215 | Hitachi
Hitachi FET To-220ab P-channel 180v 5MA 30W GSD *SS | HITACHI *SS | Distributed By MCM
Hitachi FET To-220ab P-channel 160v 5MA 30W GSD *SS | HITACHI *SS | Distributed By MCM

[scott wurcer]

Sorry guys EVUL started this so fast I was caught off guard. I hope to put up a couple of ideas later today. I don't think complexity is a goal in itself, performance is. I also don't think a design contest with an 8 transistor limit should be a prime goal.

[bcarso]

Originally Posted by dirkwright

So, some schematics a copied off a simple search. So much talk, so little action.

Number two (from post 68) is not too bad. Whose is it? It looks like something that really works.

[EUVL]

Agreed.
Nice to have, not must have (less than 8 active devices).

The same applies to extendability to a fully balanced configuration, a la OPA1632.




Patrick

[bcarso]

Originally Posted by scott wurcer

Sorry guys EVUL started this so fast I was caught off guard. I hope to put up a couple of ideas later today. I don't think complexity is a goal in itself, performance is. I also don't think a design contest with an 8 transistor limit should be a prime goal.

Eight transistors is RM's idea, although he's already relaxed things a bit by suggesting he might accept cascodes as counting as a single device, and might likewise allow current sources.

I was thinking yesterday of days of yore when transistors were dear, and PNP silicon ones were just becoming available. Some active filter papers were showing a three transistor opamp (they called it a VCVS, voltage-controlled voltage-source, as it was used for that function and typically at very low closed-loop gains). They were quite pleased at the performance attained Sort of the early Western Electric tube stuff in solid-state, and I don't doubt there are a few out there who believe that the simplicity somehow confers some sort of sonic excellence.