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Re: Pulling resistors

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  • manifold
    Some types of digital outputs can only work in one direction, they can either source or sink current but not both. Maybe an example would help, your water
    Message 1 of 2 , Dec 1, 2002
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      Some types of digital outputs can only work in one direction, they
      can either source or sink current but not both. Maybe an example
      would help, your water faucet can source a flow of water by turning
      the handle but it will not suck water back into the faucet. That is
      an example of a current source. A pull down resistor adds a small
      drain in the bottom of our example.

      In the world of electronics, is it more common to have an output that
      can sink current but cannot source any current. They are usually
      called open collector or open drain outputs. If you have a high
      output level on an open drain device, you will not see a change in
      the output voltage. A high level means that it has stopped sinking
      current but since it cannot source current the voltage remains low. A
      resistor connected from a voltage source to the output allows the
      output go to a high voltage level as soon as the output turns off.

      This is called a pull up resistor.



      --- In Electronics_101@y..., "dNixon9" <mk5852@h...> wrote:
      > Could someone explain to a struggling novice what is meant by "pull-
      > up" and "pull-down" resistors and what their functions are?
      >
      > -Mike
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