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Electric Circuits, 9th Edition P57

Electric Circuits, 9th Edition P57. Designed for use in a one or two-semester Introductory Circuit Analysis or Circuit Theory Course taught in Electrical or Computer Engineering Departments. Electric Circuits 9/e is the most widely used introductory circuits textbook of the past 25 years. As this book has evolved over the years to meet the changing learning styles of students, importantly, the underlying teaching approaches and philosophies remain unchanged. | 536 Introduction to Frequency Selective Circuits Figure 14.18 summarizes the high-pass filter circuits we have examined. Look carefully at the expressions for H s . Notice how similar in form these expressions are they differ only in the denominator which includes the cutoff frequency. As we did with the low-pass filters in Eq. 14.13 we state a general form for the transfer function of these two high-pass filters Transfer function for a high-pass filter H s - . 14.20 5 dc Any circuit with the transfer function in Eq. 14.20 would behave as a highpass filter with a cutoff frequency of coc. The problems at the end of the chapter give you other examples of circuits with this voltage ratio. We have drawn attention to another important relationship. We have discovered that a series RC circuit has the same cutoff frequency whether it is configured as a low-pass filter or as a high-pass filter. The same is true of a series RL circuit. Having previously noted the connection between the cutoff frequency of a filter circuit and the time constant of that same circuit we should expect the cutoff frequency to be a characteristic parameter of the circuit whose value depends only on the circuit components their values and the way they are connected. assessment problems Objective 2 Know the RL and RC circuit configurations that act as high-pass filters 14.3 A series RL high-pass filter has R 5 kil and 14.5 Compute the transfer function of a series RC L 3.5 mH. What is a c for this filter low-pass filter that has a load resistor RL in Answer 1.43 Mrad s. parallel with its capacitor. 14.4 A series RC high-pass filter has C 1 aF. Compute the cutoff frequency for the following values of R a 100 il b 5 kil and c 30 kil. 2 Answer a lOkrad s rc RL nnn Answer H s ----------- where K - ----- . b 200rad s 1 R -I- RL c 33.33 rad s. 5 KRC NOTE A Iso try ChapterProblems 14.13 and 14.14. 14.4 Bandpass Filters The next filters we examine are those that pass voltages within a band of frequencies .