How close to rails?

Depending on the OP-amp, I would stay within 1.5 volt of the rails. Jamie

whatever parts are to hand from scrap consumer goods, nothing will be boug ht. Question is how close to the rails can the inputs go while ensuring 90-

I'm out of date, too, but if you expect to re-use from scrap, are surface-m ount op amps really candidates? Also,can you rule out 5.5V absolute-max rated op amps?

uA741 wants 3V from any supply rail; LM307 tolerates positive-rail; LM324 a nd LM358 tolerate negative-rail, but not positive-rail; many others can go rail-to-r ail. I'd consider the LM358 and LM324 only, and (for instance) advise that any part number that is replaceable by NTE #987 is an LM324, and any part that is replaceable by NTE #928 is an LM358. As long as NTE keeps their crossr eference catalog active, that'll be some kind of guide.

se whatever parts are to hand from scrap consumer goods, nothing will be bo ught. Question is how close to the rails can the inputs go while ensuring 9

-mount op amps

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and LM358

-rail.

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sreference

Sm 8 pinners are certainly reusable. I want to avoid ruling out anything if possible, the more that can be made from available materials the better. D iffering battery voltages will be required for different opamps. Upto date information can't be counted on, people are likely to still be using data w ell over a decade old, and to use opamps that don't exist today. Info that needs regular updating won't be practical.

I think probably a simple option is to specify PSU voltages for currently p opular opamps, use dual rail supplies and accept that in many cases they wo n't function close to the rails. I think its a shortcoming that's best acce pted. I had somewhat forgotten about the old 741 and its rail hating tenden cies, I can't say I've noticed any in products in ages though.

All I need next is a list of popular opamps and I can go get data.

thanks

NT