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Lets say we have an active low pass filter with an OP-AMP. Does slew rate of this op-amp affect the filter? what will change? From what I understand, since the op-amp is charging and unchanging the capacitor with different currents passing through the resisor, there will a maximum rate of change in the output voltage, ie slew rate, which make the signal distorted.

Am I thinking correctly?

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there will a maximum rate of change in the output voltage, ie slew rate, which make the signal distorted.

This is a correct description of slew rate limit.

Does slew rate of this op-amp affect the filter? what will change?

If correct operation of your filter requires the output of the op-amp to change faster than the slew rate limit allows, then it will not operate correctly.

Notice that the slew rate depends on both the frequency content and the amplitude of the output signal. So if you have a problem with slew rate limiting, you might be able to correct it by either using lower frequencies (reducing the cut-off frequency of your LPF), or by reducing the output amplitude (by reducing the input amplitude, or reducing the gain of the filter circuit).

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  • \$\begingroup\$ Getting the bandwidth correct but forgetting the slew rate is a mistake everyone makes ONCE! \$\endgroup\$ – Scott Seidman Apr 28 '14 at 12:27
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Yes - your question touches a very imortant point. There are many people who think that - for exampe - an active unity gain lowpass filter can be used up to some hundreds of kHz if the opamps transit frequency is 1MHz or even larger. That means: Very often the slew rate limtations are completely forgotten.a

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