EGR 277

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Lecture 12 EGR 261 Signals and Systems
Read Ch. 14, Sect. 1-5 Ch. 15, Sect. 1-2 and
App. DE in Electric Circuits, 9th Edition by
Nilsson
Frequency Response This is an extremely important
topic in EE. Up until this point we have
analyzed circuits without considering the effect
on the answer over a wide range of frequencies.
Many circuits have frequency limitations that are
very important. Example Discuss the frequency
limitations on the following items. 1) An audio
amplifier 2) An op amp circuit
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Lecture 12 EGR 261 Signals and Systems
Example Discuss the frequency limitations on the
following items (continued) 3) A
voltmeter 4) The tuner on a radio
(band-pass filter)
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Lecture 12 EGR 261 Signals and Systems
Defining frequency response Recall that a
transfer function H(s) is defined as
Where Y(s) some specified output and X(s)
some specified input In general, s ? jw.
For frequency applications we use s jw (so ?
0). So now we define
Since H(jw) can be thought of as a complex number
that is a function of frequency, it can be placed
into polar form as follows
Example Find H(jw) for H(s) below. Also write
H(jw) in polar form.
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Lecture 12 EGR 261 Signals and Systems
When we use the term "frequency response", we are
generally referring to information that is
conveyed using the following graphs
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Lecture 12 EGR 261 Signals and Systems
Example A) Find H(s) Vo(s)/Vi(s) B) Find
H(jw)
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Lecture 12 EGR 261 Signals and Systems
Example (continued) C) Sketch the magnitude
response, H(jw) versus w D) Sketch the phase
response, ?(w) versus w E) The circuit
represents what type of filter?
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Lecture 12 EGR 261 Signals and Systems
Example A) Find H(s) V(s)/I(s) B) Find
H(jw)
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Lecture 12 EGR 261 Signals and Systems
Example (continued) C) Sketch the magnitude
response, H(jw) versus w D) Sketch the phase
response, ?(w) versus w E) The circuit
represents what type of filter?
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Lecture 12 EGR 261 Signals and Systems
Example A) Find H(s) Vo(s)/Vi(s) B) Find
H(jw)
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Lecture 12 EGR 261 Signals and Systems
Example (continued) C) Sketch the magnitude
response, H(jw) versus w D) Sketch the phase
response, ?(w) versus w E) The circuit
represents what type of filter?