I'm trying to design a 40dB active bandpass filter with a centre frequency of 130KHz and a passband of 80KHz. I don't really know much about filter design so I used the TI filter design tool to design one. I wanted to power the design using a single 3S lipo battery so I added a rail splitter to the design. And since the output of the filter was going to a single Ended ADC, I added a summing amplifier at the end to bias the signal by 1.65V. Here's what my final design looks like.
I designed this on a stripboard and the circuit was working so I decided to make a PCB for it. My isue currently is my PCB design is extremely noisy. I grounded the input to record the self-noise of the pre-amp and I get the following waveform (amplitude is about 600mV). I took the FFT of the signal and it seems to be at around 235KHz or so. (centre is 130KHz, 50KHz division).
The goal is to eventually design a low-noise preamp and I'll be connecting a hydrophone to it. However, right now, I'm a bit stumped as to what the problem could be. Simulation works fine, stripboard design is fine as well.
I've used 0603 package RC components but used Aluminium SMDs for the electrolytic caps. My plan is to eventually switch to tantalums in the second revision. Could anyone possibly see an issue with this?
I'm still waiting on the voltage regulator but I'm currently probing from the output of the filter.