The transistor as a switch

Discussion in 'Feedback and Suggestions' started by Unregistered, Dec 17, 2009.

  1. Unregistered

    Thread Starter Guest

    Do you have the polarity incorrect here? Current flows from + (long bar of the battery symbol) to - , thus in your example "(a) mechanical switch, (b) NPN transistor switch, (c) PNP transistor switch." the pnp and npn examples are the wrong way round.

    Mike G
  2. Wendy


    Mar 24, 2008
    You are talking conventional flow, which is actually backwards from reality. It was invented first, so as an old standard it dies hard. Electrons (the negative charge carrier) flow from the negative terminal to positive. The early chapters in the AAC text book explain this.

    A link to where you are looking always helps, and if you want to discuss this in depth register, it is free and easy to do.
    Last edited: Dec 17, 2009
  3. eblc1388

    Senior Member

    Nov 28, 2008
    I agree with the first poster.

    Current flows from positive to negative because it is a convention adopted earlier.

    Convention is convention.

    I have no trouble understanding and accepting direction of current flow and electron flow to be opposite of each other.

    However, it is misleading to draw arrow of electron flow and refer it as current flow in the associate text of a circuit schematic.

  4. Wendy


    Mar 24, 2008
    But convention is wrong in this case, we are talking reality. If you're going to teach something from scratch, you might as well go with physics vs. something invented by Ben Franklin. In many cases it doesn't matter, but in some it does. Why relearn a standard because the original is flawed but used anyhow?