After ordering and assembling one of those¹ "red" 0-30V/0-3A power supplies from eBay/AliExpress and taking a bit of a closer look at it, I'd like to replace the TL-081 op-amps. It's working fine with the specified 24VAC input, but two of the three op-amps are being powered at a total of almost 37V, definitely beyond their Absolute Maximum Rating of ±18V.
The only op-amp I've used before and know to be cheap and readily available and that handles higher VCCs (up to ±22V) is the NE5532, and that's a pin-incompatible 2-in-1.
How do I find another op-amp that is (a) still available, (b) affordable, (c) pin-to-pin-compatible, and (d) happy with, let's say, up to ±20V, so that it would work as a replacement for the above-shown circuit? Edit: as long as the other pins are a fit, I don't much care about the presence/absence of the null-offset pins (the ones which have RV1 connected to them).
Best Answer
Search parametrically, say at Digikey for op-amps in the same package, with one op-amp and that are in stock and active.
Then select ones that have dual supplies of +/-20V or more or single supplies of 40V or more. That's using the column "Voltage - Supply, Single/Dual (±)".
I suggest doing it in that order, because selecting the individual entries in voltage range is rather tedious and you want to cull the number of entries down as much as makes sense first.
When I do that, not so carefully, I get 23 types of op-amp. Sorting by price, there are only a few that cost C$5 or less each, all from TI either originally or via NS.
If you decide to make the substitution you have to look at the circuit characteristics to make sure that the new op-amps won't cause new problems and verify from the datasheet that the characteristics in the distributor parametric search are correct (sometimes they are a little wrong sometimes very wrong). Also note that not all offset trim circuits connect the pot in the same way and connecting a pot in the wrong way (even if you don't intend to use it) might destroy the chip, so again reading and understanding the datasheet and circuit is crucial.