Ac to dc

Discussion in 'General Electronics Chat' started by pinoyballer, Nov 8, 2007.

  1. pinoyballer

    Thread Starter Member

    Oct 31, 2007
    11
    0
    How do you add dc voltage to ac signal. I know how to get rid of it just use a capacitor. For example you have a 2.5 sin(400000*pi*t) input signal then i want to add a 2.5 volts to it using an op amp. the vcc and vee is 5 volts for the op amp i need a circuit to do this. thanks
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Run the AC signal into the inverting input through a resistor. Have the feedback resistor the same size for 1:1 operation - something like 20K is a reasonable value. Use a trim pot to add the offset to the non-inverting pin. The output will have the AC signal running on the DC offset.
     
  3. pinoyballer

    Thread Starter Member

    Oct 31, 2007
    11
    0
    what is a trim pot?
     
  4. pinoyballer

    Thread Starter Member

    Oct 31, 2007
    11
    0
    my out put really shrink. i dont know y
     
  5. beenthere

    Retired Moderator

    Apr 20, 2004
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    282
    A trim pot (actually potentiometer) is a small variable resistor. Also called a "trimmer".
     
  6. Distort10n

    Active Member

    Dec 25, 2006
    429
    1
    You could also use a capacitor and an inductor. The AC input will be through the cap and the DC input will be through the inductor.

    It is an easy trick to use in a lab environment. Look up 'Bias Tee.'
     
  7. pinoyballer

    Thread Starter Member

    Oct 31, 2007
    11
    0
    i dont know y the signal became .002sin(400000*pi*t)+4.882
     
  8. Distort10n

    Active Member

    Dec 25, 2006
    429
    1
    What does your op-amp circuit look like? A schematic would be nice. Looks like your are pegging one of the rails.
     
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