Filter Design

Each of the filters for the VU meters are 2nd order Sallen-Key filters. The op-amp of choice is the LM358B. The LM358B has the ability to run off a split rail and the output current should be enough for the LED arrays. The low-pass and high-pass filters were desgined first to get the values for the caps and resistors for the specific cutoff frequencies. This allowed the band-pass filter to be assembled from both filters. Side note, no testing/simulations of these filters have been done. We are flying by the seat of our pants here. I tried utilizing each op-amp in each package. This might not be the case with the actual amplification stage. A personal goal is to keep the BoM small.