video presentation on "Op Amp Applications (filters)"

Discussion in 'Feedback and Suggestions' started by xiongyw, Jul 1, 2009.

  1. xiongyw

    Thread Starter New Member

    Jul 1, 2009
    2
    0
    In the begining of the section, the instructor explained the difference between passive filter and active filter, saying that by passive filter we can only get attenuated signals (not mentioning the attenduation is in voltage/current or in power).

    I have this concern is because I just had the same question posted somewhere else regarding this, titled "Can passive filter magnify signals? ". The answer so far seems "Yes".

    http://www.electro-tech-online.com/...assive-filter-magnify-signals.html#post759455

    May be it's a better idea to get this also clarified in the presentation.

    Thanks,
    /bruin
     
  2. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    I could not find a video on your link.

    What video are you referring to?

    hgmjr
     
  3. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    What mechanism would you use to produce a gain from passive components?

    Power out is always less than power in. Power is the product of current and voltage. You may amplify the voltage, but the current will be proportionally less. The same for current. If it is increased, then the voltage will be less.
     
  4. Dave

    Retired Moderator

    Nov 17, 2003
    6,960
    145
    Thanks for the feedback. I can understand where the confusion has come in here. The point that is being made is, like beenthere has said, there is no power amplification which is trade-off between the voltage and current - points that are confirmed in the answers to your questions elsewhere.

    I do feel there is a line that is misleading to the listener. At the start of the video the speaker says, "a passive filter doesn't have any voltage or amplification". I think the reference to voltage is in terms of external voltage in the sense of that involved in amplification in a typical op amp configuration (after all this video is looking at op amp applications). The speaker does immediately go on to talk about "additional voltage and amplification" associated with active filters.

    I will try and contact Tim Feigenbaum to see if he would be willing to clarifying the points made in the video.

    Dave
     
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