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Designing Schematics for inverting 741 OPAMP

Discussion in 'Electronics Homework Help' started by citro250, Jan 21, 2014.

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  1. citro250


    Jan 21, 2014
    doing a little home project here for an opamp my cousin tells me I can make one with these components but I need to design the schematics, he tells me I can't do it but I think you can!
    help me out! :D:eek::cool:

    Single ended supply
    Power supply 9V dc at 10mA
    Output impedance: 1kΩ
    Input impedance: 2.2kΩ
    Adjustable output level: max 40dB variable resistor, potentiometer
    Frequency range: 20Hz to 20kHz +/-3dB
    Max input signal 40mV
    Max amplifier gain = 100

    It is to use a 741 op-amp in the inverting mode on a single power supply built on Vero- board

    Components given, parts list:
    22kΩ ×2
    RV1 1kΩ
    1µF ×2
    741 OP-AMP
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    Here are single supply opamp circuits you can use with the 741.

    By the way I do think your cousin is really your teacher and this belongs in the homework section.
  3. BobK


    Jan 5, 2010
    The GBP of a 741 is 1MHz, so the gain at 20KHz will be 50, not meeting your spec. Also the 741 is a very bad choice for single supply operation.

  4. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    Bob is right, the 741 is quite a bit outdated and doesn't meet the specs.

    But: -3dB at 20kHz is equivalent to a gain of 0.707 (compared to 0dB, where gain=1). Therefore max. gain of the opamp circuit in the passband (f <<20kHz) can be up to 70 (50/0.707) - still not the 100 required.
    You can design the circuit for a max. gain of 100, but then the attenuation at 20kHz will be -6dB which is a violation of another requirement.
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Well, it does specify the maximum gain.

    Designing an amplifier with a lower gain still meets the spec <evil grin>
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