opamps; single supply or dual?

Discussion in 'General Electronics Chat' started by jut, Nov 29, 2011.

  1. jut

    Thread Starter Senior Member

    Aug 25, 2007
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  2. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    "Single Supply" is usually listed under "Features"

    "Rail to Rail Outputs" should be listed as well for a good single supply op amp.

    Another tip is V+ and V- instead of V+ and GND/V- on the pinout, though that isn't shown very often.

    Supply Voltage will be listed as 0-xxV or ±xxV as well.

    Best place to look is at the top under features, as Single Supply is what a lot of circuit designers are looking for these days. Reduces a lot of cost if they don't need to build an inverting SMPS to supply a single op-amp.

    --ETA: Example - OP727 Dual Op Amp, Single Supply NOT FOR AUDIO USE
     
    Last edited: Nov 29, 2011
  3. jut

    Thread Starter Senior Member

    Aug 25, 2007
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    Thanks for the info.

    I'm experimenting with the LM1458 on the breadboard right now. The opamp is being powered with +12V and GND. It's wired up as a voltage follower (unity gain). The output follows the input, provided the input is >2V and <10V.

    So the LM1458 works with a single supply. But is obviously not a rail-to-rail op amp.
     
  4. t_n_k

    AAC Fanatic!

    Mar 6, 2009
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    You'll also note that you can't run it as an inverting amplifier unless you provide a virtual ground / reference within the common mode range. But that's not a limitation specific to this op-amp.
     
  5. crutschow

    Expert

    Mar 14, 2008
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    All op amps can be used with a single supply if you operate them within the input common-mode and output voltage swing limits. (That's how you are using the LM1458.) Since that often adds circuit complexity it's easier to use a single-supply or rail-rail type op amp for most single supply applications.
     
  6. Audioguru

    New Member

    Dec 20, 2007
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    The LM1458 is a copy of an MC1458 which is two lousy old 741 opamps in one package.
    The inputs must be 4V or more from a supply rail for the cheaper C version.
     
  7. jut

    Thread Starter Senior Member

    Aug 25, 2007
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    What do you mean by "operate them within the input common-mode limits"?
     
  8. Audioguru

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    Dec 20, 2007
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    The datasheet for every opamp shows its input common-mode limits (useable input voltage range). They are the range of voltages that the inputs work properly.

    For example the inputs of an LM741C opamp do not work properly when they are less than 3V away from the supply voltages.
     
  9. jut

    Thread Starter Senior Member

    Aug 25, 2007
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    Thanks Audioguru. :)
     
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