High-Speed Circuits and Systems LaboratoryElectronic Circuits 2
Lect. 15: Second-Order Active Filters (S&S 12.6)
Many circuit configurations for desired filter characteristics
21 2 1 2 2 2 1 2 1 1
( )(1 ) 1
KT sR R C C s R C R C K R C s
=+ + + − +⎡ ⎤⎣ ⎦
LP Filter K=(R3+R4)/R3
High-Speed Circuits and Systems LaboratoryElectronic Circuits 2
Lect. 15: Second-Order Active Filters
2
21 2 1 2 2 2 1 2 1 1
( )(1 ) 1
KsT sR R C C s R C R C K R C s
=+ + + − +⎡ ⎤⎣ ⎦
HP Filter K=R1R2C1C2(R3+R4)/R3
High-Speed Circuits and Systems LaboratoryElectronic Circuits 2
Lect. 15: Second-Order Active Filters
Op-Amp circuit can replace inductor (Antoniou Inductance-Simulation Circuit)
V1 V1
1
5
VR
11
5 4
1VV
R sC+
1
5 4 3
1 1VR sC R
11 2
5 4 3
1 1VV R
R sC R−
1 2
5 4 3 1
1 1V RR sC R R
Inductor with L=C4R1R3R5/R2
High-Speed Circuits and Systems LaboratoryElectronic Circuits 2
Lect. 15: Second-Order Active Filters
High-Speed Circuits and Systems LaboratoryElectronic Circuits 2
Lect. 15: Second-Order Active Filters
High-Speed Circuits and Systems LaboratoryElectronic Circuits 2
Lect. 15: Second-Order Active Filters
HP Filter
High-Speed Circuits and Systems LaboratoryElectronic Circuits 2
Lect. 15: Second-Order Active Filters
BP Filter
High-Speed Circuits and Systems LaboratoryElectronic Circuits 2
Lect. 15: Second-Order Active Filters
High-Speed Circuits and Systems LaboratoryElectronic Circuits 2
Lect. 15: Second-Order Active Filters
High-Speed Circuits and Systems LaboratoryElectronic Circuits 2
Lect. 15: Second-Order Active Filters
L1 = C4R1R3R51/R2 L2 = C4R1R3R52/R2
High-Speed Circuits and Systems LaboratoryElectronic Circuits 2
Lect. 15: Second-Order Active Filters
First-Order All-Pass Filter
Remember in Lect. 13V + =
V − =
1
1isCV
RsC +
2i oV V+
21i i oV V V
sRC= +
+
1 12 ( )1 2o iV V
sRC= −
+
11
o
i
V sRCV sRC
−= −
+
High-Speed Circuits and Systems LaboratoryElectronic Circuits 2
Lect. 15: Second-Order Active Filters
Second-Order All-Pass Filter
T(s)
T(s): Bandpass Filter
High-Speed Circuits and Systems LaboratoryElectronic Circuits 2
Lect. 15: Second-Order Active Filters
Second-order Bandpass Filter
Second-Order All-Pass Filter
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