No current limiter needed for 74XX chip input. Correct?

Discussion in 'General Electronics Chat' started by Mike C, Feb 11, 2015.

  1. Mike C

    Thread Starter New Member

    Feb 11, 2015
    I just wanted to confirm that I don't need a current limiting resistor on the input of a 74XX chip.

    I am currently testing on a 7404 and it seems to work fine if I connect up one of the inputs directly to the +5V power supply. Just wanted to make sure I am not risking burning out the chip. From what I can tell from reading the datasheets they have lots of internal resistors inside of them.

    Thanks and sorry if this is a complete newbie question.

    I have seen conflicting answers on the web.
  2. crutschow


    Mar 14, 2008
    As long as the input voltage is between 0V and the supply voltage there is no need for a resistor.
    I know sometimes a resistor is recommended if the input is permanently tied high to protect the input from any transients spikes on the supply voltage but I think the chances of that damaging the input are small.
  3. Mike C

    Thread Starter New Member

    Feb 11, 2015
    Thanks for the response.

    I only have 1 voltage source (i.e. I use the same rail to power the IC and to supply the HI inputs to the ic) so I guess I am ok in that case?

    Thanks a ton