a 741 simple circuit diagram

Discussion in 'General Electronics Chat' started by eliza, Feb 11, 2008.

  1. eliza

    Thread Starter New Member

    Feb 11, 2008
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    hi,
    I need a simple circuit diagram for 741 op-amp,I also need to know how to have a negative voltage ?
    thx
     
  2. Papabravo

    Expert

    Feb 24, 2006
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    1,791
    Look in the data sheet for application examples. Choose a more modern part than the 741 it was obsolete 30 years ago. A negative supply is derived from a transformer with a grounded center tap.
     
  3. SgtWookie

    Expert

    Jul 17, 2007
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    1,728
    Have a look at the attached circuits. Note the connection of two 9V batteries to obtain + and - supply voltages around ground.

    They're both configured as non-inverting amplifiers; the first one has it's gain fixed at 2:1; IE: for given input voltage, it's output is double.

    The 2nd one is variable from 1:1 to 100.1:1.

    If you look at the output from a "real" 741, you will see a phenomenon known as "phase reversal", "phase inversion" and "lockup" when the gain times input exceeds the capability of the device. Modern op amps have internal circuitry which prevent this.
     
  4. Audioguru

    New Member

    Dec 20, 2007
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    896
    If you bias the inputs properly and use coupling capacitors then an opamp does not need a negative supply.
     
  5. SgtWookie

    Expert

    Jul 17, 2007
    22,182
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    Audioguru,
    While I agree with you as far as AC signals go, that would not help the OP if they were looking at DC levels. I had to assume that:
    1) The OP is very new to op amps
    2) The circuit needed to be capable of handling anything from a DC level to the op amp's BW limitations (which in the case of the 741 is rather severe, but it's still a good exercise for a beginner. ;) )
    3) The OP needed an example of how to create a negative voltage level.

    I could have shown the use of a resistive divider across a single 9v battery, but considering the OP's requirement of a 741 demonstration, that wouldn't have left much useable headroom.

    Were the 741 an automobile, it would be a rusty 1966 Ford Fairlane with a small straight 6-cylinder engine, manual shift and patched seat covers.

    It makes one appreciate the Jaguars and Ferraris available nowadays so much more ;)
     
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