1 / 12

What is a filter Passive filters Some common filters

Lecture 24. Filters II. What is a filter Passive filters Some common filters. Active Filters. All the passive filters have a gain < 1 To achieve a gain > 1, we need to utilize an op-amp based circuit to form an active filter

cullen
Télécharger la présentation

What is a filter Passive filters Some common filters

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Lecture 24. Filters II • What is a filter • Passive filters • Some common filters

  2. Active Filters • All the passive filters have a gain < 1 • 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. Op Amp Model V+ Non-inverting input + Rout Vo Rin + – – Inverting input A(V+ –V–) V–

  4. Non-inverting Op-Amp Circuit + – + + – Vin Z2 Vout Z1 –

  5. Inverting Op-Amp Circuit Z2 Z1 – – + – + Vin Vout +

  6. An Integrator C R – + – + + Vin Vout – Earlier in the semester, we saw this op-amp based integrator circuit. What type of filter does it create? Does this help you to understand time and frequency domain interrelations?

  7. A Differentiator R C – + – + + Vin Vout – What type of filtering does it produce?

  8. Example • You are shopping for a stereo system, and the following specifications are quoted: • Frequency range: –6 dB at 65 Hz and 22 kHz • Frequency response: 75 Hz to 20 kHz ±3 dB • What do these specs really mean? • Note that the human hearing range is around 20 Hz to 20 kHz (audible frequencies) • Could you draw a rough Bode (magnitude) plot for the stereo system?

  9. Example: Building Filters via Cascade of RCL circuits Second-Order Filter Circuit Z = R + 1/sC + sL R HLP = (1/sC) / Z = Low Pass C VS + – L

  10. 15.3Ω 37.0Ω V1 L=1mH V2 L=1mH V3 C=2.5μF C=2.5μF V2(s)=H1(s)V1(s) V3(s)=H2(s)V2(s) Example: Building Filters via Cascade of RCL circuits • Example of last in-class exercise • 4th Order Butterworth • Cutoff- 20000 rad/sec • System function: • Implement each Hi(s), i=1,2 using RLC (series) circuit

  11. R R V1 L V2 L V3 C C V2(s)=H1(s)V1(s) V3(s)=H2(s)V2(s) Sectional 2nd Order Filters Connected by Voltage Follower • Op-Amp isolate sections of 2nd order circuits • Loading between sections can be kept low

  12. Class Examples • Problem 10-12 (p421).

More Related