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Current feedback Op-Amp

Discussion in 'Electronic Design' started by krw, Oct 4, 2008.

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  1. krw

    krw Guest

    I have an application for a fairly high power op-amp (50MA - 24Vp-p
    into 300ohms) at audio frequencies. For several reasons, likely
    some not very good, I selected the AD810 for a test. After doing
    some more research I'm having second thoughts about a current
    feedback amp in this application (Howland current source), though
    the simulation looks good. Specifically I'm concerned about the
    zero input impedance at the inverting input. I still have (a
    little) time to change it to a voltage feedback amp, but would
    rather not for this test. Not having been an analog type for
    <mumble> years (and having never used a current feedback amp), I
    thought I'd get the opinion here. Thanks.
     
  2. I came across this, earlier today
    http://www.national.com/pf/LM/LME49600.html
    probably overkill though

    martin
     
  3. krw

    krw Guest

    I don't have the exact schematic here, other than it's a classical
    Howland current source driving two loads (a transmission line and an
    impedance matching leg) connected as a bridged trans hybrid. My
    concern is with the current feedback amplifier in the Howland
    current source.

    I haven't thought through the ramifications of the CF amp's input
    characteristics WRT a VF amp. I'm having a bit of trouble with the
    whole concept. I guess next weeks job is wrapping my arms around
    CFAs.
     
  4. krw

    krw Guest

    Kinda neat. I'll file it away, but I don't see how it's going to
    help me here and it's kinda expensive (almost $5).
     
  5. krw

    krw Guest

    Didn't think it was that funny, though I'm out of my normal water
    here.
    I ignored it because the intended use is almost a full page left of
    the "peak". The application is audio, and not for phoolz.
     
  6. krw

    krw Guest

    Understood. Five orders of magnitude is a lot though.
     
  7. krw

    krw Guest

    Sure, but five decades is a lot of space to roll the gain off to
    below 1. A single pole squishes 100dB in that space. ;-) The
    nominal gain of this thing is only 1 (though it is in the feedback
    path).
     
  8. krw

    krw Guest

    Sure, that's what I meant by it being in the feedback path. Does
    anyone use output stages for a lot of voltage gain? Sounds
    dangerous.
    Which, to me is why that hump has "Danger Will Robinson" written all
    over it, but again, it's 5 decades away for where I care.
     
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