12–24 Astudent decided that she needed a low-pass filter that had a roll-off of –2 or – 40 dB=decade, with a cutoff frequency of 2000 rad=s. She correctly designed two identical passive RC filters, each with a cutoff of 2000 rad=s, and connected them in cascade. She cleverly separated them with a buffer to avoid loading. When she measured the cutoff frequency, she was dismayed to discover that it was not 2000 rad=s although the roll-off was correct.

(a) Simulate the cascaded pair using Multisim and determine where the actual cutoff frequency occurs.

(b) Help the student by altering her design so that the two identical RC filters actually produce the desired outcome.

Explain why the discrepancy occurred. Verify your new design using Multisim.