amplifier question

Discussion in 'General Electronics Chat' started by diwa2000@gmail.com, Jun 26, 2008.

  1. diwa2000@gmail.com

    Thread Starter Active Member

    Apr 15, 2008
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    hello guys
    can anybody please tell me why does an output of an LM741 amplifier does not completely reach the supply rails. For example in my case the supply voltages are +5/-5V and at 500mV the output is 3.36V. the gain is 10.
    Please help
     
  2. StephenDJ

    Active Member

    May 31, 2008
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    Good question, diwa! I'd like to know the answer too.
     
  3. Wendy

    Moderator

    Mar 24, 2008
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    There isn't a secret about it, the datasheet of a 741 also includes the chips schematic. Basically it is the output short circuit protection, which makes the chippie so useful for beginners.

    You have to realize how old this chip really is. The fact it is still so useful is a testament to the designers.
     
    Last edited: Jun 26, 2008
  4. blocco a spirale

    AAC Fanatic!

    Jun 18, 2008
    1,440
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    I'm not convinced that the 741 is such a good device for beginners. I know it appears in many textbooks but it can be difficult to use due to requiring split rail supplies and of course its inability to get anywhere close to the supply rails. Is it unity gain stable? probably not. There are lots of modern op-amps available which exhibit near ideal behaviour and are suited to low voltage single-rail battery power applications.

    Anyone inexperienced in electronics could easily waste a lot of time going round in circles trying to figure out why their circuit isn't behaving as expected when in fact the problem is due to the limitations of the 741.
     
  5. SgtWookie

    Expert

    Jul 17, 2007
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    If you want the output to reach the supply rails, you will have to use a much more modern op amp.

    Look at AD8051, LM6132, LM6152, LMH6642, OP179, there are many others.
     
  6. Audioguru

    New Member

    Dec 20, 2007
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    The lousy old 741 opamp is 40 years old this year. It was designed to use positive and negative 15V supplies, its max output was +13V and -13V, its high level response was from DC to only 9kHz and its high noise level is not spec'd.
    May it rest in peace.
     
  7. JoeJester

    AAC Fanatic!

    Apr 26, 2005
    3,373
    1,159
    As long as the 741 is useful ... it will remain. It's deficiencies show up very easy on lower bandwidth scopes to illustrate the problems one can encounter.

    Other than the training enviroment, I would agree, may it rest in peace. I think it will be around for quite some time though.
     
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