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Op Amps - non-inverting

Discussion in 'Electronics Homework Help' started by JasonMcG, Jun 6, 2014.

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  1. JasonMcG


    Mar 2, 2014

    Need help with the following problem and how to go about it.

    Consider a non- inverting amplifier circuit of a closed loop gain of 48. The input to the amplifier is an ac input signal of 100 mV at 1 kHz. The non-inverting amplifier is implemented using the LM 324 and the device parameters are specified to be: Aol = 100 V/mV; Vio = 7.0 mV, IIB = 300 nA, Iio = 100 nA, and SR = 0.4 V/μS. Given that the input resistor is 10 kΩ, and the power supply is ±15 V, do the following:
    i) For an uncompensated design, determine the output voltage and the maximum dc offset error at the output of the amplifier. [5]
    ii) Determine the magnitude of the offset minimizing resistor. [2]
    iii) For a compensated design, determine the maximum frequency of the input voltage for which the output is not slew rated. Assume that the effect of error due to input offset current on the peak output voltage can be neglected.

  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Excellent question.

    Show us how far you've progressed.
  3. LvW


    Apr 12, 2014
    Jason, before starting to solve the task you have to be informed about the meaning of the various mentioned parameters (Aol, IIB, Iio, SR, compensared/uncompensated). Are you?
  4. JasonMcG


    Mar 2, 2014
    Aol is your open loop gain.
    Vio is your input offset voltage.
    Iib is your input bias current.
    Iio is your input offset current.
    SR is your slew rate.

    For i) I found Vo(vio) to be 48 * 7mV = 336mV.
    Not sure if this is correct.

    I'm not looking for answers but ways to go about solving this problem and op amp problems in general as I am looking to learn
  5. Arouse1973

    Arouse1973 Adam

    Dec 18, 2013
    Hi Jason
    So first thing to do is work out your gain setting resistors. So have you been told how to do this?
  6. JasonMcG


    Mar 2, 2014
    No I'm not sure how to do that
  7. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    Perhaps you can start with a drawing of a non-inverting amplifier with just an op-amp and two resistors. You're familiar with that, right?

    Then check your notes for diagrams where these two resistors labelled Ra and Rb, or R1 and R2 (or similar) and where you have also noted a formula that involves either the ratio between them, or the ratio of one to the sum of both.
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