help regarding single rail opamp use

Discussion in 'General Electronics Chat' started by ashrok, Feb 22, 2009.

  1. ashrok

    Thread Starter Member

    Feb 22, 2009
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    hi all,
    i need help in opamp usage,
    I'm using this LM741 in single 5V supply..The purpose is to shift the DC level of input signal.
    If the signal is 5Vpp wit DC value at 0V(from -2.5 to +2.5V).
    I shd shift this signal to +ve side b/w 0 and 5V with DC at 2.5V..
    Is this possible?

    if not, is there any other way to do this,
    pls help

    thanks in advance,
    A
     
  2. mentaaal

    Senior Member

    Oct 17, 2005
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  3. Wendy

    Moderator

    Mar 24, 2008
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    You'll need to use a different op amp, that is way under what a 741 can use for power supply. A LM324 might work.
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    You won't get there using a 5v supply with an LM741. If you're lucky, you might get 1v peak to peak output with a 5v supply. LM741's were the greatest thing since sliced bread, when they were introduced some 40+ years ago. They are still around because professors like to punish their students with them. ;)

    Increase your Vcc to 10v, or use an opamp that has rail to rail inputs and outputs, like an LM6132.
     
  5. mentaaal

    Senior Member

    Oct 17, 2005
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    I hear that! I am one of those students!
    Our lecturer had marked vcc and ground pins wrong on our schematics and in the space of a few minutes a whole class's worth of opamps were blown!
     
  6. Wendy

    Moderator

    Mar 24, 2008
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    There bye allowing him to buy new op amps, or get closer to that goal.
     
  7. SgtWookie

    Expert

    Jul 17, 2007
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    Nope. Voh for an LM324 is Vcc-1.5v for a 2k Ohm load. He'd need an absolute minimum Vcc of 6.5v.
     
  8. ashrok

    Thread Starter Member

    Feb 22, 2009
    13
    0
    hey thanx a lot guys..i cant believe i missed out such a simple concept of summer.
    thanx again..
    yes i had some doubt about using lm741(went ahead as v had worked wit tis IC in all the labs)..
    i'll chk out on lm324.
     
  9. ashrok

    Thread Starter Member

    Feb 22, 2009
    13
    0
    actually i cant use supply voltage greater than +5V. We take power from USB port of the PC. so max allowed is +5V. that is why we thought of using the op amp in single rail mode.
     
  10. bertus

    Administrator

    Apr 5, 2008
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    Last edited: Feb 22, 2009
  11. SgtWookie

    Expert

    Jul 17, 2007
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    Take a look at ICL7660 and MAX1044 IC's; they are CMOS switched-capacitor voltage converters. They can give you a low-current dual +5v/-5v or +10v supply from a 5v source.

    http://pdfserv.maxim-ic.com/en/ds/ICL7660-MAX1044.pdf
     
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