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Explore the characteristics of circuits like low-pass, high-pass, and band-pass filters, and learn about system modeling and responses in physical systems. Visualize plots showing magnitude and phase responses for various filters and equivalent circuits. Discover the behavior of noisy sinusoidal voltages through filter circuits such as Wheatstone bridge and RC filters.
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C H A P T E R 6 C H A P T E R Frequency Response and System Concepts
I L S S 1 + + V V 2 L S L CD Player Amplifier Speakers – (Source) (Circuit) (Load) A physical system A circuit model Figure 6.1 A circuit model I
RC low-pass filter. The circuit preserves lower frequencies while attenuating the frequencies above the cutoff frequency, = 1/ RC . 0 The voltages V and V are the i o filter input and output voltages, respectively. R + + V C V i o _ _ Figure 6.9 A simple RC filter
1 0.8 0.6 Amplitude 0.4 0.2 0 2 1 0 1 2 3 4 10 10 10 10 10 10 10 Radian frequency (logarithmic scale) Phase response of RC low-pass filter 0 _ 20 _ 40 Phase, degrees _ 60 _ 80 10 10 10 10 10 10 10 Radian frequency (logarithmic scale) Figure 6.10 Magnitude and phase response plots for RC filter Magnitude response of RC low-pass filter
Filter capacitor c R T + V R R _ noise 1 3 + a b + V V _ V V C T out a b _ C + _ V R R S 2 4 Wheatstone bridge equivalent circuit d _ V = V V out a b Figure 6.14 Wheatstone bridge with equivalent circuit and simple capacitive filter
Noisy sinusoidal voltage 10 5 Volts 0 _ 5 _ 10 0 0.08 0.16 0.24 0.32 t (s) Filtered noisy sinusoidal voltage 10 5 Volts 0 _ 5 _ 10 0 0.08 0.16 0.24 0.32 t (s) Figure 6.15 Unfiltered and filtered bridge output
RC high-pass filter. The circuit preserves higher frequencies while attenuating the frequencies below the cutoff frequency, = 1/ RC . 0 C + + V V R i o _ _ Figure 6.16 High-pass filter
1 80 0.8 60 0.6 Amplitude 40 0.4 20 0.2 0 0 – 2 – 1 0 1 2 3 4 – 2 – 1 0 1 2 3 4 10 10 10 10 10 10 10 10 10 10 10 10 10 10 Radian frequency (logarithmic scale) Radian frequency (logarithmic scale) Figure 6.17 Frequency response of a high-pass filter Phase, degrees
RLC band-pass filter. The circuit preserves frequencies within a band. C L + + V V R i o _ _ Figure 6.19 RLC band-pass filter
Band-pass filter amplitude response 1 0.8 0.6 Amplitude 0.4 0.2 0 10 3 10 2 10 1 10 0 10 1 10 2 10 3 Radian frequency (logarithmic scale) Band-pass filter phase response 50 Phase, degrees 0 _ 50 10 3 10 2 10 1 10 0 10 1 10 2 10 3 Radian frequency (logarithmic scale) Figure 6.20 Frequency response of RLC band-pass filter
R L 1 i ( t ) O + v ( t ) v ( t ) C R i 2 C – Z Z 1 L + V ( s ) V ( s ) Z I ( s ) Z i C C O 2 – Figure 6.32 A circuit and its Laplace transform domain equivalent
6 4 2 Imaginary part 0 – 2 – 4 – 6 – 10 – 5 0 5 Real part Figure 6.33 Zero-pole plot for the circuit of Figure 6.32