TTL Logic Questions?

Discussion in 'Homework Help' started by RightytoLefty, May 19, 2009.

  1. RightytoLefty

    Thread Starter New Member

    May 11, 2009
    A circuit is using 2 parallel open collector outputs to drive some TTL inputs, the more inputs you add:
    1) the LOW- level current that may be allowed to flow through the pull-up resistor increases
    2) The High-level current that flows through the pull-up resistor decreases
    3) the pull-up resistor has a smaller range of acceptable values
    4) th High-lever open collector outputs must source more current to the inputs

    My next questions is:
    Which one of the statements is FALSE:
    1) A TTL LOW level output sinks current from a connected TTL input
    2) A High level totem pole output sources current to a connected TTL input
    3) a High level open collector output coureces curent to a connected TTL input
    4) a Low level TTL input sinks current from a +5 V through the base of a input transistor

    I know these may seem simple enough but until I can fully grasp what is going on in these circuits questions like these give me a problem. Thanks for the help in advance. I have read quite a bit about these circuits but it just hasn't clicked yet but I will keep grinding but I need some help.
  2. bertus


    Apr 5, 2008