Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Diode OR Gate - the role of resistor

  1. Feb 24, 2007 #1

    dobry_den

    User Avatar

    Hi! What would happen if the resistor in the attached diode OR gate removed (connection with the ground would be preserved)?
     

    Attached Files:

    Last edited: Feb 24, 2007
    dobry_den, Feb 24, 2007
  2. jcsd
    Phys.org - latest science and technology news stories on Phys.org
  3. Feb 24, 2007 #2

    berkeman

    User Avatar

    Staff: Mentor

    It ensures that the output is low when both of the inputs are low. Without the resistor, the output voltage would be undefined in that case.
     
    berkeman, Feb 24, 2007
  4. Feb 24, 2007 #3

    dobry_den

    User Avatar

    What do you mean by the word "low".. like when the inputs are of zero potential, when they're grounded? In that case the output would be also grounded and therefore defined... Or am I mistaken?
     
    dobry_den, Feb 24, 2007
  5. Feb 24, 2007 #4

    ranger

    User Avatar
    Gold Member

    In digital logic, a logic zero or low would occur when the input is somewhere in the range of 0 - 2V. Its probably less than 2V, that varies depending on technology being used. For TTL devices, I believe it 0V-0.8V for a logic zero.

    The output is always grounded via the resistor i.e. the output is voltage drop across the resistor and not taken directly from ground.
     
    ranger, Feb 24, 2007
  6. Feb 25, 2007 #5

    dobry_den

    User Avatar

    ok, thanks a lot. Another problem occurs when I am about to calculate the current in the output - should I take the output branch and the resistor-ground branch as connected in parallel?
     
    dobry_den, Feb 25, 2007
  7. Feb 25, 2007 #6

    ranger

    User Avatar
    Gold Member

    Yup. The current through the resistor is not the same current going to the load connected to the output. The voltage however is the same.
     
    ranger, Feb 25, 2007
  8. Feb 25, 2007 #7

    dobry_den

    User Avatar

    Ok, that makes it clear. Thanks
     
    dobry_den, Feb 25, 2007
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Diode OR Gate - the role of resistor

  1. Diode Gate Electrical Network (Replies: 3)

  2. Diode AND Gate - Voltage Drop (Replies: 7)

  3. Two Diode AND Gate - New to EE (Replies: 15)

  4. Gate Resistor, Rg in JFET (Replies: 3)

  5. Diode running into the resistor (Replies: 14)

Loading...