[sdiy] LM741 substitute

[Magnus Danielson]

JH. wrote:
> Nothing is flawless.
> Every opamp has its flaws, and not neccessarily the same flaws as another 
> type.
> Before you substitute an opamp type in a circuit, make sure that the design, 
> that obviously was made to live with the flaws of the chosen opamp type, 
> will also work with the flaws of the opamp of your choice.
> 
> The TL071 is no drop-in replacement for a 741. Far from it, actually.
> 
> The EMS circuit Magnus referred to goes one step further than working around 
> flaws:
> It makes a clever use of the opamp's internal circuit, shutting down part of 
> it. Granted, that's not using the opamp concept - it's transistor level 
> design, using some of the transistors readily integrated in a cheap, 
> available chip.

That's how I recall it. Disabling parts of it while using others. Stuff 
almost any other opamp in there and it will fail misserably. Not that it 
is the ideal way to go around making the design these days, but when you 
encounter it, 741 is the only one know to pull it off, for better or 
worse. The 741 is still out there and still does some jobs just as good 
as it did back in the days. Nothing else is called for. However, there 
is a few more op-amps around these days than when the 741 hit the 
streets. Back then you had to work around the limits that you had and 
live with it. If you didn't have high-Z inputs, you put the FETs there 
so you got it etc. If you needed better noise you added a new set of 
input transistors for that purpose. The op-amps still save you alot of 
design-effort and component dollars, even when they did not match the 
criterias correctly. Modernizing these designs with modern op-amps cuts 
lots of components. However, you also change character. Increase the 
comparator-gain of your oscillator core, and you have a different 
oscillator.

Cheers,
Magnus