Op amp advice

Discussion in 'The Projects Forum' started by paulsoulsby, Apr 18, 2014.

  1. paulsoulsby

    Thread Starter New Member

    Jan 9, 2013
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    I need an op amp suitable for reducing the output voltage of a PWM pin of an Arduino.

    It needs to have this spec:
    • Input Voltage 0-5V
    • Output voltage 0-1V (inverting or non-inverting)
    • rail to rail
    • single +5V supply (no -V supply)
    • frequencies 20-20kHz
    • DIP package

    I thought this would be quite a simple spec to achieve but am really struggling to find anything.
    The OPA342 would have been perfect, but it doesn't come in a DIP package. Is there anything similar in a DIP package?
    many thanks
    Paul
     
  2. tshuck

    Well-Known Member

    Oct 18, 2012
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    Is there a reason a voltage divider wouldn't work?
     
  3. paulsoulsby

    Thread Starter New Member

    Jan 9, 2013
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    I also need it to act as a buffer (so next part of circuit sees it as approx 0 ohms resistance).
    I could potentially use a voltage divider followed by an op amp as a buffer. Just thought it'd make sense to do it all in the one circuit.
     
  4. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
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    380
    hi,
    Look at the MCP6002, its a dual rail to rail OPA , in DIP
     
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  5. tshuck

    Well-Known Member

    Oct 18, 2012
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    Ah, we get more information.;)

    Pretty much any single supply, OP amp can do this. You can find tons by going to Digikey and searching for those parameters. You can even exclude anything other than DIP packages...
     
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  6. paulsoulsby

    Thread Starter New Member

    Jan 9, 2013
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    Ah yes, I'd already looked at that and ruled it out because I thought input was limited to –1.0V to +1.0V.

    But I'd misread it and it's actually VSS – 1.0V to VDD + 1.0V (so -1V to 6V), so it's perfect!!

    Thanks very much!
     
  7. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
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    Use a divider on the non inv input set for 5/1 and configure the MCP as a non inverting buffer
     
  8. tshuck

    Well-Known Member

    Oct 18, 2012
    3,531
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    Since you are outputting into a low-impedance speaker (I'll assume), make sure the op amp can handle the power requirements.
     
  9. paulsoulsby

    Thread Starter New Member

    Jan 9, 2013
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    0
    OK will give that a try thanks.

    It's to output either to headphones or a powered input on a mixer. So nothing too bad. I'll check the spec sheet.
     
  10. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,540
    1,251
    Sounds like you're using the Arduino as the front end of a class D amp or synthesizer. Note that the pwm frequency and an output filter between your buffer and the load are critical to sound quality. You might wind up configuring your buffer as a 2-pole lowpass filter. Nyquist, Shannon, and Fourier all apply here.

    ak
     
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