Design an op amp-based low pass filter with a cut off frequency of $500 \mathrm{Hz}$ and a passband gain of 1 using a $50 \mathrm{nF}$ capacitor.
a) Draw your circuit, labeling the component values and output voltage.
b) If the value of the feedback resistor in the filler is changed but the value of the resistor in the forward path is unchanged, what characteristic of the filter is changed?