Triangle vs. Ground: What's the difference?

Discussion in 'General Electronics Chat' started by Rogare, Mar 20, 2012.

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  1. Rogare

    Thread Starter Member

    Mar 9, 2012

    In the AD633AN datasheet, there is a diagram for "Squaring and Frequency Doubling" (p. 8). In the diagram there are ground symbols used at pins 5 and 8, but triangles used at pins 2, 4, and 6. What's the difference?

  2. PatM

    Active Member

    Dec 31, 2010
  3. MrChips


    Oct 2, 2009
    Look at post #5 on this thread:

    You will see three symbols for ground, Signal Ground (Common), Earth Ground and Chassis.

    Earth Ground is used for electrical safety.
    Chassis is the metal box of your equipment. This is wired to Earth Ground through the GREEN wire (in North America) on the 3-wire AC cord.
    Signal Ground or Common is the 0V reference point in your circuit. If there is no connection to Chassis Ground, then your circuit is "floating".

    It is common practice to connect Signal Ground to Chassis Ground.

    There should be no current flowing from Signal Ground to Chassis Ground to Earth Ground.
    MaxHeadRoom likes this.
  4. Rogare

    Thread Starter Member

    Mar 9, 2012
    OK, thanks for the replies—much appreciated.

    I built the circuit, but it didn't turn out as expected: for a 3V input, I was expecting a 0.9V output, but got about half of that. For a 0.5 input, I was expecting a 25 mV output, but the DC offset alone was 40 mV. (The output should be Vin^2/10.)

    So, I think I may not have understood the grounding correctly. The circuit I built is diagrammed in "My Circuit.jpg" and the reference from the AD633 datasheet is in "AD633 Reference.png." Does anything seem glaringly off?

    (Minimum operating range for the chip's supply voltage is +/- 8 V.)
  5. BillB3857

    Senior Member

    Feb 28, 2009
    I would insure that both batteries are supplying exactly the same voltage. If the supply is unbalanced, output will loose accuracy.
  6. Rogare

    Thread Starter Member

    Mar 9, 2012
    OK, I'll do that. Does the grounding look OK? I'm still a bit unsure about which type (triangle vs. parallel lines) are used where.
  7. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    I believe the different ground symbols are intended to keep noisy things away from quiet things. Typically such a scheme is used for a "digital" (noisy) and "analog (quiet) ground.

    Try connection all the grounds together at one point, meaning one wire between them on the board you have. The grounds still need to connect, just at one point to prevent circulating currents bouncing off ground.

    ("circulating currents bouncing off ground" is not quite a technical description but I pray it gets the point across.)
  8. Rogare

    Thread Starter Member

    Mar 9, 2012
    OK, yes, that makes sense. Thanks!
  9. studiot

    AAC Fanatic!

    Nov 9, 2007
  10. leonalee

    New Member

    May 17, 2015
    Maybe too late but it useful to the users, check out below source, good source to find of which symbol and what about it is.

    Last edited by a moderator: Jun 28, 2015
  11. MaxHeadRoom


    Jul 18, 2013
    And a pet peeve of mind as a few previous posts will attests to.
    I have always taken issue with the likes of the 'Art of Electronics' as using the earth ground symbol throughout the book.
    Where IMO it should be either chassis or logic common, unless they specifically wanted to indicate the common is earthed.
    Last edited by a moderator: Jun 28, 2015
  12. Wendy


    Mar 24, 2008
    Tsk Tsk, necroposting and hijacking at its worst. Both are not really allowed here.
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