Sallen Key LPF-modified w Bode plot

This Sallen Key LPF, modified with a resistor in series with feedback cap, has been set up to test out a Bode plotting method. By using an FM chirp input, we can sweep a frequency across the freq range of interest, and observe in the grapher, the output response. This gives us the amplitude and phase response of the LPF, though you have to zoom in and measure the freq and phase at the point of interest manually...like in the good old days.