Other Parts Discussed in Thread: OPA140
I' m designing a circuit of a band pass filter + adder . Can we design the BPF and adder using a single opamp? I have space constarints neeed to reduce the number of opamps
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I haven't seen that done before, but there may be a way to do it. I assume the BP filter input is an AC signal. What are the filter characteristics and what frequency range is of interest? When you mention "adder" what are you trying to add an AC or DC signal, and to what are you trying to add it to?
My thought is a multiple feedback (MFB) or Sallen-Key BP topology might be able to be applied with a summing input at the other input; the one where the various R and C components do not connect back to. For example in OPA140 datasheet, Figure 8-1, 25-kHz Low-pass Filter, a voltage could be applied to the now grounded non-inverting input. An input applied to that input would have a different gain and transfer function than that applied through the inverting filter input path so thought would be required to do that and have things function as needed.
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