Replacement part for LMV821

Discussion in 'General Electronics Chat' started by NewStudent, May 13, 2008.

  1. NewStudent

    Thread Starter Member

    Feb 16, 2008
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    I need a replacement part for the LMV821 - 5MHz, Low Voltage, Low Power, RRO, 5 MHz Op Amps. The LMV821 only comes in a SC70-5 and I need a DIP.

    Any suggestions?
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    Is this a homework assignment?
     
  3. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
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    Go to a site like Linear or TI and do a parametric search.
     
  4. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    Fairchild Semiconductor has a pretty good parametric search engine as well.

    Mouser.com also has a decent parametric search - and it's cross-vendor.
     
  5. NewStudent

    Thread Starter Member

    Feb 16, 2008
    25
    0
    Hi SgtWookie

    No, this is not an homework assignment. I'm trying to build a souped up ultrasonic range finder.

    I found this circuit at:
    http://www.edn.com/index.asp?layout=article&articleid=CA45965

    I thought I'd build and test it's performance, but I can't locate the LMV821 in a DIP package so I need an equivalent. I've searched the web, read a lot of data sheets, and found the TS1871 and the LM6132. Unfortunately, I don't know enough electronics to recognize what parameters are necessary for an equivalence for this application.

    Secondarily, the schematic fails to identify T1 specifying only 200:8. I recognize the symbol for a transformer. Does the 200:8 represent a winding ratio? Does the 200 side connect to the transmitter? Can I buy this part or do I need to make it?

    Thanks for the help

    p.s. What is a parametric search?
     
    Last edited: May 13, 2008
  6. SgtWookie

    Expert

    Jul 17, 2007
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    OK, just checkin' ;)
    They sure come up with some intriguing ideas - and some really goofy ones, too!
    Why not go with an LMV821? Just design a circuit board for it, and make provisions for the pads. The dimensions are right there in the datasheet. Then solder that bug right to the board!

    You can use an audio output transformer; 200 Ohms on one side, 8 on the other. Yes, it's a ratio of turns. Radio Shack doesn't stock a suitable transformer; the only one they carry is 1000:8. You could wind your own if you were ambitious or bored. Or you could buy one from someplace like Mouser or perhaps a salvage place or online auction for a couple of bucks.

    You supply the parameters you want to search for, and click "search"
     
  7. Papabravo

    Expert

    Feb 24, 2006
    10,152
    1,794
    In my mind, at least, there is some ambiguity on the 200:8. It could be either a turns ratio OR an impeadance ratio. IIRC the impedance ratio is the square of the turns ratio.

    If it was a turns ratio it could have been expressed as 100:4 or 50:2 or 25:1. If it was an impedance ratio then there must be something about the values 200 and 8 that you can identify in the external circuit.

    I suppose you could email the magazine or the sauthor seeking a clarification.

    Good luck I hope you figure this one out.
     
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