A pull-up resistor is used to raise the input level of electronic circuits with a DC voltage level. Such a pull-up resistor is connected to the operating voltage and biases the input of an active circuit or a logic circuit
with this voltage. In a sense, it raises the input level to the operating voltage level.
resistorThe control of such a biased logic is done by switching the input to ground potential via a transistor or a switch
. In this case, the pull-up resistor loses its function, which it only performs again when the switching function is interrupted or the switch is open. Logic gates can be constructed with pull-up or pull-down resistors that perform the complementary function.