Circuit symbols

Discussion in 'Homework Help' started by totalnewbie, Jun 5, 2009.

  1. totalnewbie

    Thread Starter New Member

    Jun 4, 2009
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    Hello. I haven't found any good reference materials pertinent to showing how to draw circuits in different ways. Please look at the attachment. There are three colored rectangles. The one is red - I haven't figured out what it means. It isn't even connected with the circuit? Why is this part of circuit important to this circuit at all? What does these red rectangles mean? Are they called terminals? Does the left one mean the input voltage (so that left one is connected with battery which isn't depicted on the drawing)? Does the right one mean the output voltage (so I can connect that output point with whatever element I want)? How to understand the red one? It doesn't seem to be the ground. Please try to explain it in plain english because I haven't taken any electronics course, just trying learn it by myself.
     
  2. Gokee2

    New Member

    Jun 5, 2009
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    I don't know a whole lot myself but that looks like a basic op amp circuit to me. Left box is input right is output and your green one is ground. Power to the op amp is not shown.
     
  3. mik3

    Senior Member

    Feb 4, 2008
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    Don't worry about the squares in the circuit. Maybe they are used by the circuit explanation to show something.

    Ve= input voltage. The arrow points to the positive side of the voltage (source)

    Va=output voltage. The arrow points to the positive side of the output voltage.

    In both cases the arrow points to ground. This means that the input and output voltages are negative with respect to ground.
     
  4. David Bridgen

    Senior Member

    Feb 10, 2005
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    The arrows do not signify polarity. They simply mean a voltage with respect to the common line (your "ground").

    It's an inverting amplifier.
    With a negative input there will be a positive output.
    With a positive input ...... do I need to go on?

    The colours have no standard significance. They're just a whim of the person drawing the circuit or who had a hand in the software with which it was drawn.
     
  5. studiot

    AAC Fanatic!

    Nov 9, 2007
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    One of the arrows is drawn in the wrong direction.
     
  6. mik3

    Senior Member

    Feb 4, 2008
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    If you are making circuit analysis it doesn't really matter.
     
  7. studiot

    AAC Fanatic!

    Nov 9, 2007
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    I realise the signs in the arithmetic will take care of themselves MIK, but I like to write things down correctly where I can, it's an inverting amp so a positive going input will generate a negative going output.
     
  8. Wendy

    Moderator

    Mar 24, 2008
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    This is a case where context matters. It is an illustration taken out of context.
     
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