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Why no H11F1 OptoFET?

Discussion in 'Electronic Components' started by Lostgallifreyan, May 20, 2007.

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  1. The H11F1 is (was) multisourced, Fairchild, Isocom, and possibly others.
    I bought 20 from Digikey only a few weeks ago. Now they have none in stock,
    and a recent poster here says he got a mail from Digikey announcing that
    Fairchild will stop making them (not that they ever did, they bought out
    the maker QT Optoelectronics, and now seem determined to bury this part).
    RS Components list them for sale, made by Isocom, but on Isocom's site that
    part and also H11F2 and H11F3 optoFET's have vanished with no trace that
    they ever made any.

    Despite recent changes to make them RoHS compliant, suggesting that full
    production was intended to continue, this optoFET seems to be vanishing the
    way of the Norwegian Blue. Anyone know why? If a component is good enough
    that more than one company wants to make them, how is it that they can all
    vanish as if some weird and surprisingly effective conspiracy was shutting
    them all down at once? I'd like to know what could account for it, and what
    could be used instead.

    Most of all, I must know why and how such a thing can happen. It doesn't
    make sense to specify any but the most enduring and commonplace parts in a
    design if something as established as this can be torn down in a week or
    three without notice. I've seen several people here complain of this kind
    of thing, and it seems to be getting worse.
     
  2. Guest

    NTE lists a crossover of NTE3085... Web-tronics.com shows them in
    stock, as well as weisd.com. Tried plugging it into Digikey with no
    avail. Mouser shows in-stock with their part number 526-NTE3085.

    Hope this helps.

    -Gordon
     
  3. Eeyore

    Eeyore Guest

  4. Thankyou. It does, a lot. As these IC's are expensive, (even H11F1's are in
    UK, the last were bought via a friend in the US), I'll only buy a few as I
    need them so I need to know I can get them again. If I can, I can get by.
    What's scary is the thought that something as useful as a FET optoisolator
    could vanish as if suddenly no-one thinks they are useful. Google shows
    many inventive uses for them, but if the makers decide they don't value any
    of that, it helps to know why they should not do so. I can't see how
    something with such a unique and powerful function could be replaced or
    made obsolete.
     
  5. So do RS. But for how long? I'm not thinking about the few drying pools
    left, I can raid a couple of those if I need (and I will, as the NTE3085
    that Gordon posted about costs at least double). I didn't raise a new
    thread to find a handful, but to question what looks like the end of the
    line for something that showed every indication of being new. It reminds me
    of a news story about a village that grew daffodils for a show, and whose
    occupants woke one morning to find someone had cut all the buds off during
    the night. This obviously isn't the dying end of an old product no-one
    needs anymore, so what's going on?
     
  6. Guest

    It concerns me as well... but that's the way of the world anymore. I
    remember a time when you could get pretty much anything you wanted at
    RadioShack... but the RadioShack of today is nothing like what it was
    ten years ago. Used to be once upon a time that people were excited
    about this hobby, and you saw all sorts of incredible and inventive
    things being done. All of that's gone now. The beancounters have
    taken over. Electronics isn't sexy anymore.... so if some large
    corporation isn't buying them by the tens of millions... the profit
    margins are too low to even bother with catering to a virtually
    nonexistent hobbyist market.

    Expect to see lots of handy things disappear as time goes on... and as
    modern manufacturing moves more and more toward SOICs and ASICs...
    expect to see our hobby relegated to the complete, utter fringes of
    society.

    Glad I could be of help.

    -Gordon
     
  7. Eeyore

    Eeyore Guest

    But are they sensible uses ?

    If its possible to do it with a cheaper part you can be sure that's what will
    happen. No demand for the part and it'll be discontinued.

    The days of designers using boutique parts have vanished mainly. What
    application are you using them in ?

    Graham
     
  8. Yes. Go look at the H11F1 datasheet, that alone shows some uses that make
    them worth saving.

    Your talk of 'boutique' parts in this case is stupid. If you beleive that
    logic you'll soon be advocating the censure of mere fripperies like the
    thyristor and the triac.

    You shouldn't need to know my application to justify the need to retain
    such a part, and I shouldn;t have to tell you. What do you seek to do? Ask
    me to puty it up su you can knock it down? The makers didn't need your
    justification to make the part in the first place, so why does your
    judgement now depend on mine? For your curiosity, I will answer: a laser
    diode modulator. And don't tell me there is an easier or cheaper way to get
    a shunt modulator that has excellent isolation and linearity than this,
    because there isn't one. An optoFET is the only way to do that cheaply with
    a very low parts count. I've seen other designs in lots of commercial
    designs, and most of them are horrible. In their effots to be cheap they've
    reduced all the safety and linearity they want to brag about, and one
    little optoFET could have made a LOT of difference.
     
  9. Eloi and Morlocks. >:) This wouldn't be the first time I've been reminded
    of those. Wells was right.
     
  10. Eeyore

    Eeyore Guest

    Whose ?

    I was hoping you'd say which ones were sensible in your assessment.

    Hardly. They're used by the bucketful.

    Because I'm curious why you need it and maybe I could have offered another
    solution.

    You're getting a bit pissy over a simple question here. If you don't want to
    tell me, that's fine.

    Graham
     
  11. Whose do you think? Did you read any previous posts on this, or did you
    drily insert your arid scholarly wit in the assumption that you know FAR
    too much to actually read a post before answering it?

    FAIRCHILD. That would be a good start.
    What is this, a masterclass?? Try the sample/hold with very low leakage and
    no feedback to the controlling system, or the noiseless AGC/switch/fader
    for audio, or the isolated laser diode modulator.
    No, I'm getting pissy over your dry aura of scholasticism that has no
    grounds for its high and mighty airs. And I did tell you. I guess you
    didn't read that either.
     
  12. Not interested. I'm not so blind I can't see alternatives, or that your
    offer is really based on your desire to show that I'm wrong. Don't bother.
    If you want to impress, show why the makers of that IC, Isocom, Fairchild,
    and the form NTE that have emulated it and justify more than double the
    cost see fit to make them in the first place. If you can show why all those
    people are wrong, I'll be mightily impressed, believe me.
     
  13. Eeyore

    Eeyore Guest

    I was asking you. You didn't specify and I don't believe in making guesses. How
    about specifying which uses you think are uniquely suitable to opto-fets ?

    Graham
     
  14. Eeyore

    Eeyore Guest

    It could very easily be.

    I have no application for that. The absence of charge injection is cute but
    everything else could be done in any pratical application I can think of with
    simple level shifting.

    It's fairly rubbish for audio. More than about 75mV rms across the fet and you
    get distortion. VCAs do much better and for ages I've also been using
    opto-coupled resistors. These are vey nice and a lot cheaper (as little as 20
    cents in China) and even match quite well.

    Graham
     
  15. Eeyore

    Eeyore Guest

    More like practical real world low-cost design experience. I DO NOT use silly
    frivolous pricey boutique parts.

    You remind me of the guys (so-called designers) who would get all excited over
    RS introducing some new exotic expensive part into their catalogue who then felt
    obliged to design it in to their employer's products and design the company into
    financial failure.

    Graham
     
  16. Eeyore

    Eeyore Guest

    I rather doubt that. They probably picked up some equivalents and just re-marked
    them, RS components style.

    Because they could ?

    Wrong about what ? Once upon a time there was demand and they made a profit.
    That's good business. If there's no demand now they'll stop making them. That's
    good business sense.

    Incidentally, if you look at the applications on the Fairchild data sheet, many
    are analog. Much of that is done in DSP now. I can't imagine anyone making a
    filter tuned with opto-fets these days when you can do the same thing more
    accurately with better THD and noise figures and cheaper too in DSP.

    Also, if you must, these optically coupled resistors are about 20 cents....
    http://www.sbcds.com.cn/en/Products.asp?Cid=172

    Graham
     
  17. Guest

    Dude... seriously. Go take a prozac or something. I get the
    impression Eeyore is only trying to help.
     
  18. Given only two or three firms mentioned, and one that comes up for most
    Google results, you didn't have to guess, you had to think.

    As for 'unique': unfair question, and you know it. There are often other
    ways to do things, the question is which is best. A lot of things justify
    this part type, as the makers obviously realised. If a lot of people choose
    not to use them, fine, but when you want the resistor-like behaviour of a
    FET without the complications of a bipolar type, and the total electrical
    isolation that this part offers, an optoFET is the best part to choose.

    You're asking the wrong question. Instead of asking me why the part should
    exist, ask the makers. All of them. They can answer better than I ever can.
    All I ask is that having made them, I'd like to know why they might stop,
    having gone through RoHS adjustments in a clear effort to continue, and
    what replacements might be found. Gordon chose to help, you chose to argue.
    I accepted the invite, but it gets old fast. If I'm to argue further I want
    it to be with some better reasoning and attention than you've shown.
     
  19. Wrong. I try to use basic parts where possible. I just happen to consider
    an optoFET as a basic part, just as a bipolar optoisolator is a basic part.
    I don't like using new unusual parts with complex or exotic special
    functions either, but you can't see that can you? All you can see is
    someone who knows less, therefore must know virtually nothing. You're all
    judgement, but so inattentive of stuff in the posts you're answering, that
    you look more ignorant then you should.
     
  20. I don't. I felt like arguing with him. Your help was useful. His wasn't.
     
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