I am designing a 40 kHz bandpass filter for a university project involving a portable ultrasonic device. I have designed a 40 kHz filter using the Linear Technology Filter Design Tool with a single rail op amp (due to design being powered by 9 V battery, stepped down to 5 V using LF50 voltage regulator). The circuit was then built in LTSpice and simulated using an AC sweep. Below is the LTSpice circuit as well as simulation results, which are exactly as desired. (Note: LTC6255 used in simulation, MCP 601 used in actual circuit.)
The circuit was then built on stripboard and tested using a AFG-2105 function generator to perform an AC sweep from 1 Hz to 100 kHz with Vpp = 7 mV. A Picoscope was used to read the waveform.
As you can see, the test results do not come close to the simulated results.
Any ideas what I might be doing wrong?
I checked ground connections, retested and got the following result: