1. Lecture 241 EEE 302 Electrical Networks II Dr. Keith E. Holbert Summer 2001

2. Lecture 242 Active Filters To achieve a gain > 1, we need to utilize an op-amp based circuit to form an active filter We can design all the common filter types using op- amp based active filters Recall for an ideal op-amp that V + = V – I + = I – = 0

3. Lecture 243 Class Example Extension Exercise E12.19

4. Lecture 244 Inverting Op-Amp Circuit – + V in +–+– + – V out Z2Z2 Z1Z1 V out = – (Z 2 /Z 1 ) V in

5. Lecture 245 Noninverting Op-Amp Circuit V out = (1 + Z 2 /Z 1 ) V in + –+ – V in +–+– V out Z1Z1 Z2Z2

6. Lecture 246 Op Amp Model + – Inverting input Noninverting input R in V+V+ V–V– + - A(V + –V – ) VoVo R out

7. Lecture 247 PSpice Design Example Let’s design an active filter in PSpice using Problem 12.69 to start –Determine the type of filter –Use goal function to find the filter cutoff freq. Now replicate/expand the circuit from above in the fashion shown in Problem 12.70 to form a higher order filter –Use goal function to find the filter cutoff freq.