Frequency Responses

1
Frequency Responses

• Up to now, we have learnt
• ac circuit analysis with periodic sources (fixed
  frequency, if multiple frequencies, use
  superposition principle)
• Transient analysis
• Now, frequency responses filters and resonant
  circuits.

2
Transfer Function
Since we are interested in frequency responses,
we use phasors (frequency domain). VL(jw) is a
phase-shifted and amplitude-scaled version of
VS(jw)
3
Filters

• Low-pass filters (LP)

4
Low-Pass Filters

• Break frequency wwo1/RC, HV1/?2
• working example
• quick determination of filter type

5
Build other filters by combing impedance
6
Concept Check filter
Which of the following circuits is a low-pass
filter?
Answer (c)
7
High-pass Filters (HP)
1/?2
8
Concept Check filters
Which are the following circuits high-pass or
low-pass filters?
Answers High-Pass Filters (b) and
(c) low-pass filters (a) and (d)