741 opamp data sheet help

Discussion in 'Homework Help' started by Random3s, Nov 2, 2014.

  1. Random3s

    Thread Starter Member

    Jul 30, 2014
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    Hi,

    I am writing a report concerning inv and non inv op amps. The inverting op amp circuit was 18v, + or - 9v and the amp was able to swing within a couple of volts to the supply rails, at around 7v max. I understand this is usual behaviour for 741 op amps, but would like to know what its referred as on the data sheet. Below is a link to the 741 model iam using, but I cant find anything in the sheet to confirm this behaviour. I am not sure it would be enough to state that "commonly 741 opamps are able to swing within a volt or 2 of the supply rails".

    Thanks in advance.

    LM741 data sheet
     
  2. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Read the fairchild datasheet.
    There is this graph given:

    [​IMG]

    Bertus
     
  3. Jony130

    AAC Fanatic!

    Feb 17, 2009
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  4. Random3s

    Thread Starter Member

    Jul 30, 2014
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    Thanks guys, so the voltage output swing is provided as a ratio of a given supply to a set RL value. In this case is RL the feedback resistor, from the output back to the inv input? (standard inv and non inv amp config)?

    Could someone also point me in the right direction with regards to the bandwidth of a 741, there isnt a badwidth stated in the data sheet, but my project build had a break freq of 6kHz.

    thanks again
     
  5. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    Normally RL is LOAD RESISTOR, from output to ground.
     
  6. bertus

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    Apr 5, 2008
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    Hello,

    The philips datasheet has a graph for the frequency versus gain:

    [​IMG]

    Bertus
     
  7. shteii01

    AAC Fanatic!

    Feb 19, 2010
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  8. Jony130

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    Feb 17, 2009
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    Yes, without RL resistor, feedback resistor is a load for opamp

    Well, the data sheet give as Gain bandwidth product = GBP and additional if we know the voltage gain we can find breakdown freq.
    For example for non-inverting amplifier with gain equal to 10V/V we have
    Fc = GBP/10 = 1MHz/10 = 100Khz but for inverting amplifier with a gain equal to -10V/V we have
    Fc = GBP/( 1 + |10|) = 1MHz/11 = 90.9kHz .
    And for voltage follower we have
    Fc = 1MHz/1 = 1MHz but for inverting amplifier (gain -1V/V) we have Fc = 1MHz/ (1 + |1|) = 500KHz

    Of-course this is true only if we have no capacitors across Rf resistor or parallel to the load resistor.
     
    Last edited: Nov 2, 2014
  9. Random3s

    Thread Starter Member

    Jul 30, 2014
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    Great, thanks for your help guys, much appreciated.
     
  10. WBahn

    Moderator

    Mar 31, 2012
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    For the data sheet you linked in the OP, there is a line for Output Voltage Swing that lists the swing for various supply voltages and load conditions. It also supplies a bandwidth spec based on rise-time measurements (be sure you read the Notes in datasheets). This is most likely the gain-bandwidth product for an opamp.
     
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