Re: 'pullup' resistors


"Simon Scott"
Hey all

Complete noob here - so can someone explain the concept of 'pullup
resistors'?

Im looking at the data*** for the 74LS07 and it says 'the open
collector
outputs require external pullup resistors for proper logical
operation'.

As Pauline Hanson said, 'please explain'?

http://www.seattlerobotics.org/encoder/mar97/basics.html

The output of the buffer is not capable of supplying a voltage, it can
only pull the pin to ground. In order to provide a high level output, a
resistor must be used to "pull up" the pin to Vcc (supply voltage).

.