Op Amps

Discussion in 'Feedback and Suggestions' started by Unregistered, Dec 28, 2009.

  1. Unregistered

    Thread Starter Guest

    Dear Sirs I just read through the tutorial about op amps.
    To my understanding the figures (and some text) on

    http://www.allaboutcircuits.com/vol_3/chpt_8/5.html

    should have the 6 mA current going in the oposite direction from what is depicted, as the positive current will 'seek' its way to a lower potential.

    Please correct,

    Best regards,
    Rui
     
  2. Unregistered

    Thread Starter Guest

    Well with regard to my last message I just noticed that in the treated problem there are instances where the current follows the rule I enunciated (go to low potential) and instances where it does not. I'm puzzled. To me it would seem that through R1 flows a current coming from the amplifier?! This can't be right. What's wrong?
     
  3. Unregistered

    Thread Starter Guest

    Please ignore the last comment.
     
  4. Wendy

    Moderator

    Mar 24, 2008
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    This textbook uses electron flow, current flows from negative to positive. That being the standard I believe the drawings are correct.

    The difference was explained very early in this textbook, where the convention for the rest of the book was set.

    http://www.allaboutcircuits.com/vol_1/chpt_1/7.html
     
  5. steveb

    Senior Member

    Jul 3, 2008
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    It's amazing how many of these comments come in here. It shows how firmly rooted the positive current convention is.

    I'm always tempted to say that it would be better to use the positive current convention just to avoid all the comments, but I suspect just as many comments would come in, (although from a different group) if it were changed.

    Perhaps a footnote disclaimer on every page would help, but then there would be complaints about how stupid it is to keep repeating such an obvious thing.

    I feel this is the classic "no-win" scenario! :p
     
  6. Wendy

    Moderator

    Mar 24, 2008
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    Yeah, (knowing I'm preaching to the choir) it matters. I have a little process at work for gold wire bonding. It uses an arc to melt .001" wire from an electrode that moves into position, charges and discharges on the wire (melting it into a tiny ball), and move out of the way again.

    They chose the wrong direction for the current early in the process, causing ions of metal from the electrode to travel to the gold ball, causing problems. They had to redefine the process, it is now called negative EFO. My point is, the actual direction of travel for the electrons matter in this process.

    In the real, physical world electrons exist, and it matters which way they move.

    Classic triode tubes (valves) are another example, how can anyone understand them without knowing how real current moves?
     
  7. Wendy

    Moderator

    Mar 24, 2008
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    Thinking about it, it might be worth a sticky to that effect.

    To the moderators and administrators, whatcha think?
     
  8. beenthere

    Retired Moderator

    Apr 20, 2004
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    I thought the Ebook got into electron flow a.k.a. current early on - http://www.allaboutcircuits.com/vol_1/chpt_1/2.html

    That is probably the best we can do, although I'm not at all against a sticky note.

    If we can invent a time machine, one Benjamin Franklin is going to get a visit....
     
  9. nubelube

    New Member

    Jan 3, 2010
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    As someone who is new to the book, I think the sticky would be useful. I suspect that many people like myself don't read the book from beginning to end, but rather skip to sections of interest. As such, they are likely to miss the convention notice.

    As a physics-person, I always hated the positive charge convention, but I had accepted it as a fact of life in the electronics world. I didn't even realize that there was a strong contingent of electron-flow people. Thus, while experienced electronics people might look at the diagrams and quickly realize the convention, less experienced people (who are unaware that there is a choice to be made) are likely to be confused unless there is a prominent warning of the convention.
     
  10. beenthere

    Retired Moderator

    Apr 20, 2004
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    Said sticky now exists...
     
  11. nubelube

    New Member

    Jan 3, 2010
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    Ah, ok. I was thinking of a sticky-like object in the actual book rather than in the Feedback/Corrections forum. I think a prominent (frequently repeated) notice in the book would be useful...but it's not my book so I'll keep my mouth shut. :)
     
  12. Wendy

    Moderator

    Mar 24, 2008
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    Books are pretty static, and assume the reader goes through it one page at a time. You have to remember the AAC book is basically meant to be in paper format, we offer it in several electronic forms (including PDF, which will create a really good paper copy) to allow the users to have online references.

    We have a lot of people who are convinced that conventional is the right and only way to portray it, even some old hands around here. This is why the sticky was locked, there are those who enjoy arguing endlessly on the subject.

    Physics and electronics are locked together, much of electronics is basic physics. The base structure of an atom and electrons are pretty well understood, and this theory directly conflicts with conventional theory, so why mess with a flawed standard?
     
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