Op-Amp Based Band Pass Filter

Equivalent Circuit @ DC

(DC feedback)

Equivalent Circuit @ ω=ωo

Circuit Analysis

(Solve for Vout/Vin)

Circuit Analysis

Second Order Bandpass Filter

Bandwidth of Second Order Bandpass Filter

Circuit Parameters

Matlab Script

Cadence Simulation

Tunable Bandpass Filter

BPF at 100 Hz12.396 mS

15.15 mS

Vout is delayed by 2.76 mS, approximately ¼ of a period.

Closer Look at 950 Hz

(Vout is larger than Vin!)

BPF at 10 KHz

Question

• What is tunable?– Not a capacitor! (Not an absolute

requirement, since you can always do switches to add/remove capacitors)

– Resistor, but which resistor? Consequnce?• R3+R4• R1• R2