I put together a notch filter from the info @matt posted and needed a split power supply for the opamp that followed it.
Matt showed some 10uf and .1 uf caps to split it but even after matching them closely, I got uneven results. I went instead to using a couple 100k resistors and a single supply LM358 to create the split power supply for the opamp following the notch filter. Any thoughts on whether those high value resistors and LM358 will be adding much noise to the notch filter? Thx for any thoughts.
I am not sure this will help at all, but It does use a single supply to power the opamp. It generates both a “normal” and inverted signal to be used for bridging a power amp…
Thx @VAR. I was trying to keep parts to a minimum in order to keep noise down.
This is what I did but wondered about noise from the 100k resistors and op amp.
@matt had shown the capacitor divider in the lower right on this but even carefully matching cap values I had trouble balancing voltages and things went badly when I loaded the output with the op amp follower to the notch filter in the second circuit diagram.
Here is the notch.
Not sure if it makes any difference, but “my” circuit used 10K instead of 100k resistors.
@VAR forgive my ignorance as a untrained 70+ year old. So are you biasing the input up to +6v instead of providing a split supply to the opamp?
Hi Moto. That is a pretty ambitious circuit to undertake so you must be doing pretty well at 70! I am in my 60’s and still learning a lot. Looking at what I sent you was was looking at it wrong. The TL072 opamp normally runs off a dual supply, but in this case it is running off a 12V, with a 10ohm resistor to limit the current. The 15v zener and 220uF cap are there since the circuit was designed for use in a car. The -Vcc is set to ground. I am not sure if the circuit will work for your needs with the LM358…