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LM358A for high-side current sensing

Discussion in 'Electronic Basics' started by Hammy, Jul 13, 2008.

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  1. Hammy

    Hammy Guest

    I'm using an LM358A for high-side current sensing. I would like to be
    able to use the other OP in the so-8 package as a thermal shutdown.
    This means that both outputs would be connected to the same point R9&
    R8 junction on the schematic. Q1 &Q2 are really a dual prebiased
    MUN5311DW1T1-D I'm using as a latch.

    Schematic

    http://i37.tinypic.com/2z9csja.png

    My question is do I have to place blocking diodes on the output of the
    OP'S. If one output goes high it will place Vcc-1.5V on the output of
    the other OP will this damage the OP?



    I don't have any LM358A's on hand but I would like to be able to test
    it with maybe a TLC27L2 so the same question for this OPAMP.

    Thanks
     
  2. neon

    neon

    1,325
    0
    Oct 21, 2006
    how are you going to get [-] anything out of your circuit ii see vcc and gnd. why try to reinvent the wheel try lm317 aand throw this away.
     
  3. Jamie

    Jamie Guest

    I would feed the R4 Via the extra OP-AMP. Also, I don't think you'll
    get a full high side out on this op-amp. This may not be a problem in
    your case how ever since the normal operation of your circuit would
    require it to hold the output low in which case it looks like it should
    do well.
    I would how ever, use a hysteresis feed back in the (+) input to make
    sure you don't develop a linear region at the critical point, this could
    upset the current regulation a bit unless you don't want a latching
    effect protect circuit.






    http://webpages.charter.net/jamie_5"
     
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