Opinions: On op amp replacement

[Martin Czech]

I'd say:

LF41x    etc. for low offset and offset drift, rel. low leak
NE553x   for high bandwitdh, low noise
TL07x    for rel. low noise, low leak
CA3140   low leakage
TL08x    else

I really would like to test "very low" leak types like CA3140
against TL07x or LF041x.

The 3140 has mosfet inputs, but ESD-Protection diode junctions as well,
if Ta max is set to 45C, how much more leakage would a 41x or a 07x 
take ? Is it really an order of magnitude ? I doubt. 
And the data sheet also. And the 3140 has certainly a lot of disadvantages.

Old schematics (and our concepts are all very old) suffer from the fact,
that at THAT time no other ICs existet. Today one should consider using
something better.

Of course, a clone is a clone, better stay to original hardware then.

But: semiconductor manufacuturers change masks without notice,
it is very doubtfull if a 1978 3140 is really the same as some 3140
from today, even worse with second source products.

Circuits that rely on parasitic effects may not even work
with todays hardware, even if the stamp code says "3140".

m.c.