OP-61 Replacement Op Amp

Have you considered buying an SFP module?

The OP doesn't say whether it is free-space or fibre. If its fibre, then SFPs are incredibly cheap for a lot of convenience.

John

Thanks all, I'm looking lower level than the SFP modules, but thanks for your comments.

What do you actually mean by "lower level"? Power, complexity or something completely different? Are you using fibre or free space? If fibre is it glass or plastic? What distance? Without knowing what you are actually trying to do it is very difficult to offer useful help. John

I think that's an equivalent statement to, "I don't know". I don't get why people make things hard by asking questions that would only matter if you were going to change the design. The guy asked for an op amp replacement. That seems pretty clear to me.

If you want to know more of the details that are important, that would be reasonable to ask. What band width is required? What input current is acceptable, etc...

So Spencer, what are the important specs of the op amp for your design? I'm not familiar with TIA circuits, unless you mean transient ischemic attack, which I highly doubt.

Not at all. Lower level means lower level, anyone doing design work knows what it means. And the guy has been quite clear what he needs - a replacement for the OP-61. Last night I did look at the parts I have used and I saw none which would be a direct replacement, it would take some real work for me to find one which I don't have the time for.

Spencer, the closest I can suggest it an AD829 *but* it settles to only 0.1% rather than 0.01 and it has about 10 times the input current. Has been good for me for many years, but probably not good enough for you. The OPA637 comes sort of close but is slower to settle to 0.01%. I vaguely remember some current feedback parts, AD846 or something, but I am not sure if that one was in the ballpark you need, apart from not knowing if a current feedback part is usable in this case at all. And I have only played with it, not used it (unlike the other two I mentioned).

====================================================== Dimiter Popoff, TGI

LT1222 looks like it might be a good replacement, availability isn't fantastic but likely better than the OP-61:

if you're only building one...

Thanks for the suggestions all... This is my first time designing a front end for a digital system, so I'm still trying to figure out what 'analog' considerations I can forgo. In the digital world, I think I need to worry less about input current noise since I will quantize the output, but that doesn't seem to get me much in terms of broader amplifier selection.

I'm looking at the OPA856, built for Lidar applications.

It always seems a crime to me that the parts >10 years old all fall into obsolescence... Especially from the companies bought by TI, ADI. It can't be a coincidence that all the BB/LT/etc parts are the first to go and with no replacements.. Do they discontinue the parts because they want us to buy their fully kitted modules, or is there really just no market?

Thanks again, Spencer

That one sure looks good bet there are also many others with up to 5V supply which will do. The one you initially considered is a +/-15V part.

I don't have many complaints about Analog obsoleting their parts, I can still get opamps I designed with 30+ years ago. Anything has a limited lifetime of course.

The OP-61 is in my 1990 PMI databook. (PMI used to write _beautiful_ datasheets.)

Cheers

Phil Hobbs

There are multiple reasons parts are obsoleted. Post-acquisition product line duplication is certainly one, but not the only one by a long measure.

Fabs are expensive things to run. Depending on the process, wafers can cost from hundreds to many thousands of dollars each. Companies look at the revenue per wafer. A product that's filling up the fab but not making much profit is not going to survive long. Same with a low-selling product that requires one wafer lot per many years - there are costs associated with holding inventory.

Another concern is equipment and supply obsolescence. Not many companies are running 4" silicon wafer fabs these days (are any?) The equipment is obsolete and unmaintainable, and I'm not even sure wafers are available. So if company A purchases smaller company B, and B is using end-of-life equipment, B's low-running products are unlikely to get transferred to a newer fab process as there are very large costs is making such a transfer. Even within the same fab, a newer process may supplant an older one and it may not be worth the expense to migrate low-runners to the newer process.

Companies generally announce a product's demise and offer lifetime buys to their customers. Big customers will get individual notifications, the smaller ones have to constantly be on alert for this information.

Produce obsolescence is unavoidable. Technology evolves and markets change. The buggy-whip industry isn't what it once was, and Ford is no longer making the Model T. Nor is Intel making the 8080 or 80286.

"That's a Burr-Brown part, nobody knows anything about it."

That's an issue born of normal retirements, layoffs, internal transfers, job changes to other companies, and early retirements (buyouts). The cost of supporting something "forever" are very high.

In this particular case, BB was acquired by TI 22.5 years ago. Their processes and equipment were older than that.

TI is about the best at keeping old parts in production. I wonder what they do about test sets.

Maxim was the worst. They would discontinue parts at the sampling stage. There were part numbers that the people wouldn't even admit to. We learned about EOL on MAX9690 when the parts never showed up. Maybe ADI will run things better.

I haven't seen many Richardson parts lately. Is there a story?

Richardson or Rochester?

piglet

Rochester I guess. They bought old wafers and maybe masks to keep parts alive. I used to see them on Digikey a lot.

Richardson is an RF parts distributor.

Rochester keeps coming up in Digikey searches for me. It's a bit irritating really--there's a $300 line item minimum for everything they sell.

Cheers

Phil Hobbs