It's a very general question and the application is unclear. Are you referring to radio frequency work ...? Perhaps you could provide some more details.
It's for an ultrasonic rangefinder on the receiver end to put an amplifier or a bandpass filter first (with center frequency around 40kHz). I did some reading about it and found out that it's common to amplify and then filter.
How about an amplifier configured as a bandpass amplifier? It's just an amplifier stage with limited frequency response. That way, the signal amplitude doesn't descend into the depths of the background noise and it still gets some frequency limiting applied to it.