Designing a Second Order Passive LPF: Tips and Insights

  • Thread starter Thread starter ACLerok
  • Start date Start date
  • Tags Tags
    2nd order
Click For Summary

Discussion Overview

The discussion revolves around the design of a second-order passive low pass filter (LPF). Participants explore the challenges faced in achieving the desired cutoff frequency and the implications of using passive components in filter design.

Discussion Character

  • Technical explanation, Debate/contested, Homework-related

Main Points Raised

  • One participant is seeking insights on designing a second-order passive LPF, noting difficulties in achieving the correct cutoff frequency when cascading two RC circuits.
  • Another participant suggests considering an active filter instead, highlighting the advantages of using op-amps for greater design flexibility and gain.
  • A third participant indicates that the assignment specifically requires a second-order passive LPF, expressing frustration over the lack of responses to the initial query.
  • A later reply mentions a different assignment involving a third-order high pass RC active filter, indicating a broader context of filter design challenges among participants.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus. There are competing views on the merits of passive versus active filters, and the original question regarding the design of a second-order passive LPF remains unresolved.

Contextual Notes

The discussion reflects limitations in the understanding of passive filter design, particularly in relation to achieving specified cutoff frequencies. There is also a dependence on the specific requirements of assignments, which may restrict design choices.

ACLerok
Messages
194
Reaction score
0
This isn't really an exact homework problem since it's for a report I'm doing. Basically, I was wondering what the design for a second order passive low pass filter looks like. I know how to design a regular first order circuit but I have no clue about a second-order PASSIVE LPF. I tried just cascading two RC circuits and using 1/(2pi(RC)) to define the cutoff frequency but after simulating it on my computer, the actual cutoff is quite off. Anyone have any insight into this?? Thanks in advance.
 
Physics news on Phys.org
Why do you want to make a passive filter? Take my advice and use an active filter. The techniques for making active filters using op amps is very mature and you can get whatever gain you wish. Look for the book on the web (its free!): "Digital Signal Processing" by Steven Smith. Look on page 50 for a good discussion on analog filters and a simple design table.
 
Believe me, I would, but it tells me to make a 2nd order passive LPF in the assignment. Thanks though.
 
Shame there was no answer to this forum :( I am stuck now too I have to do a 3rd order high pass RC active filter though
 

Similar threads

Replies
6
Views
3K
Replies
13
Views
5K
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 43 ·
2
Replies
43
Views
7K
  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 27 ·
Replies
27
Views
3K
  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 11 ·
Replies
11
Views
4K
Replies
3
Views
3K
  • · Replies 5 ·
Replies
5
Views
2K