Diferent Op-Amps

Discussion in 'General Electronics Chat' started by Iodem_Asakura, Jun 26, 2005.

  1. Iodem_Asakura

    Thread Starter Senior Member

    Sep 14, 2004
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    Are there diferent Op-Amps? Someone told me that some Op-Amp ICs only works as comparators, so can't be used like inverter amplifiers (ex. LM339). Is that true?

    So are there Op-Amps that can be used only in some configurations and not in others?
     
  2. hgmjr

    Moderator

    Jan 28, 2005
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    iodem_asakura,

    Yes, There are two types of operational amplifiers available to the electronic circuit designer. One is the classical operational amplifier whose output is a voltage that is proportional to the difference between the voltages applied to its positive and negative inputs. The second type of operational amplifier goes by the name operational transconductance amplifier or OTA for short. For the OTA, the output is a current that is proportional to the difference between the voltages applied to its positive and negative input terminals.

    All operational amplifiers can be used in the various gain configurations (inverting, non-inverting, etc.)

    There is another type of device that shares the same schematic symbol as the operational amplifier. This device is a voltage comparator. The LM339 is this type of device. The voltage comparator is a classical op-amp on steroids. Its gain has been deliberately designed to be as high as possible so that just the least difference between its positive and negative input will drive the output voltage to its maximum output voltage in the positive or negative direction. This high gain comes at a price. The high gain involves more gain producing stages inside the device. These additional gain stages introduce a delay between the voltage change at the input and the corresponding voltage change at the output. This delay makes the voltage comparator unsuitable for use as an operational amplifier.

    Although you cannot use an voltage comparator as an op-amp, there is nothing to prevent the use of an op-amp as a voltage comparator.

    I hope this explanation is helpful.

    hgmjr
     
  3. Iodem_Asakura

    Thread Starter Senior Member

    Sep 14, 2004
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    Yes, that was a great explanation.

    How can i identify each one by the datasheet?
     
  4. hgmjr

    Moderator

    Jan 28, 2005
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    The datasheet should clearly identify the type of device in its title.

    hgmjr
     
  5. Iodem_Asakura

    Thread Starter Senior Member

    Sep 14, 2004
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    Thanks, i already saw it. Thanks for all.
     
  6. rd_aec057

    New Member

    May 2, 2005
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    can anyone suggest a better site for understanding opamp in a better manner
     
  7. pebe

    AAC Fanatic!

    Oct 11, 2004
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