Active filters are a common and extremely useful, they come in so many varieties, it can become confusing. What about the terms “Butterworth”, “Chebyshev” or “Bessel” when applied to filters? Do you know what they mean?
Noise in active circuits like op amps as well as Johnson noise, there is shot noise (charges crossing PN junctions) and flicker noise (with impurities in the channel/charge recombination)
All electronic circuits are affected by noise which is defined the unwanted disturbances in an electronic signal caused by physical phenomenon in the components themselves.