40kh filter

[imanpakii]

hi frinds i'm working on ultrasonic sensors and i have problem with 40 kh filter when i use band pass filter ,the out put have signal with no input my design attach to this post

 

[Resqueline]

Design seems ok (w/o having calculated anything) but if the gain is very high then noise can be amplified into an output signal.
Did you test it in real life or in a simulation?
An unfortunate circuit layout could turn a tuned amplifier into an oscillator.
Do you have an oscilloscope so you could trace where the problem starts?