D *14.72 Design a fifth-order Butterworth low-pass filter that has a 3-dB bandwidth of 10 kHz and a dc gain of unity. Use the cascade connection of two circuits of the type shown in Fig. 14.29 and a first-order low-pass circuit (Fig. 14.8). Use a 10- kΩ value for all resistors. Second-order section: R1 = R2 = 10 kΩ, C3 = 492 pF, C4 = 5.15 nF; Second order section: R1 = R2 = 10 kΩ, C3 = 1.29 nF, C4 = 1.97 nF; First-order section: R1 = R2 = 10 kΩ, C = 1.59 nF