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.
Transfer Function Since we are interested in frequency responses, we use phasors (frequency domain). V L (j ) is a phase-shifted and amplitude- scaled version of V S (j ) CD PlayerAmplifierSpeaker (Source) (Circuit) (Load) VSVS ZSZS Z1Z1 Z2Z2 ZLZL
Filters Low-pass filters (LP)
Low-Pass Filters Break frequency o =1/RC, H V =1/ 2 working example quick determination of filter type
Build other filters by combing impedance
Concept Check: filter Which of the following circuits is a low-pass filter? (a)(b)(c) Answer: (c)
High-pass Filters (HP) 1/ 2
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)