Page 149 - Analog and Digital Filter Design

1 46 Analog and Digital Filter Design

References

1. Stephenson, E W. RC Active Filter Design Handbook. New York: John
Wiley & Sons, 1985.

2. Winder, S. “The Real Choice for Active Filters.” Electronics World and
Wireless World, September 1993.

Exercises

4.1 A normalized inductor value is 0.8212. Denormalize this for a passive
lowpass filter having a load resistance of 5Oohms and a cutoff fre-
quency of 20 kHz. What is its denormalized value?
4.2 A normalized capacitor value is 0.5532. Denormalize this for a passive
lowpass filter having a load resistance of 600ohms and a cutoff fre-
quency of 100kHz. What is its denormalized value?

4.3 What happens to pole locations in the S-plane as the frequency is
scaled?
4.4 A second-order Butterworth filter has poles at -0.7071 f j0.7071. What
are the two capacitor values for a normalized Sallen and Key active
filter (let R1 = R2 = 1 Q)?

4.5 For the active filter in Exercise 4.4, let the resistor values equal 1 kR.
What are the capacitors’ values (C1 and C2) if the cutoff frequency is
10 kHz?