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Op amp gain and number of stages

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David Hess:

--- Quote from: Kleinstein on May 04, 2019, 09:11:23 pm ---There are mainly 2 limitation for how much gain can be used in a single stage: 1 is the GBW, as more gain reduces the bandwidth. The 2 nd limitation is the loop gain - this can be important for high accuracy. With higher gain it is harder to correct nonlinearity of the amplifier. This may limit the useful gain to something like a factor of 100 in some cases - often even a gain of 1000 is OK in 1 stage.
--- End quote ---

There is a third limit.

Over wide bandwidths, which can be 10s of MHz for operational amplifiers and sometimes less, too much gain can result in oscillation from parasitic feedback from the output to the input.  Multiple stages help here because each stage can be more readily physically isolated from adjacent stages.  Neutralization is sometimes used.

This limit also applies to radio receivers and one of the reasons for the superhetrodyne topology which divides the gain up into different intermediate frequencies.

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