Operational amplifier highest gain restriction in practical case

Discussion in 'General Electronics Chat' started by Lahari, Jul 5, 2012.

  1. Lahari

    Thread Starter New Member

    May 30, 2011
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    Is it possible to get gain of 1000 in a LM324 or OP07 practically? If not why? What gain can an OPAMP provide maximum? Why this restriction?
     
  2. WBahn

    Moderator

    Mar 31, 2012
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    All opamps have an open loop gain, which is the absolute most gain you can get.

    Opamps also have what is known as a gain-bandwidth product (GBWP). At least to first order, if you double the gain, then you can only get half the bandwidth. An LM324 has a GBWP of about 1MHz, so at a gain of 1000, you are only going to get a bandwidth of about 1kHz.

    There are other considerations as well. You have a maximum slew rate (in the case of an LM324 it is about 50V/ms). Also, depending on the circuit it is a part of, getting a gain of 1000 may end up requiring component values that are too high or too low for the opamp to deal with well.
     
  3. t06afre

    AAC Fanatic!

    May 11, 2009
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    But it is fine to have say 3 gain stages in cascade with a gain equal to 10. The total gain will then be 10x10x10. Each stage can also be implemented as 2. order filterstages as an extra bonus
     
  4. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    Once I needed a 60dB amplifier for a 3 MHz signal. Hey, wouldn't you know 60dB is also a gain of 1000 times?

    GBWP was a severe restriction at such a high frequency. The solution was to use a dual amp to get 2 gain stages. Each had a gain of around 32 (as 32 x 32 = 1024).
     
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