Week 10 (03/11-03/18)

• Worked researching bandpass filter design.

• Single supply design didn't work as expected, I had to redesign the circuit and figure out a way to get negative voltage.

• Prof. Young Suggested using a 555 timer to get the negative voltage, I was able to get negative voltage to supply to the Op Amp. using the following circuit:

• Initially I used the resistor and capacitor values shown on this referenc

• This gave me significant electromagnetic noise because the astable multivibrator was set to a frequency of 9khz which is within the audible spectrum .

• I changed the resistor values to the ones shown in the schematic, thus getting a 33khz frequency, well beyond the audible spectrum.

• I had to redesign the bandpass filter design. thus I used the following and thested the whole assembly in the bench.

• The circuit above corresponds to a Sallen-Key Low-Pass Filter paired in series with at passive HPF at the output. The first pot controls the frequency, the second controls the amplitude of the lowpass filter cut.