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Current Limiting Resistor and Pull-Up Resistors

Writer:Microhm Page View:Date:2019-08-12
A current limiting resistor is the one used to reduce the current present in a circuit. A simple example is a resistor in series with a LED. You would usually want to have a current limiting resistor in series with the LED to control the amount of current flowing through it, else the LED will burn due to it exceeding its current limit. Microhm Electronics shunt resistors, like MMS2512, can be used for this application.

Pull-up resistors are resistors commonly used in logic circuits to help ensure a well-defined logical level at a pin under all conditions. It is used to prevent the logic state to be left as “floating”. The pull-up resistor solves this problem by pulling the value to a logical high state when switch S1 is open instead of leaving it floating.
Pull-up resistors are not a special kind of resistors, they are simple fixed-value resistors connected between the voltage supply and the appropriate pin, which results in defining the input or output voltage in the absence of a driving signal.
Pull-down resistors work in a similar manner as a pull-up resistor, except that they pull the pin to a logical low value. They are connected between ground and an appropriate pin on the device. Pull-down resistors must have a larger resistance than the impedance of the logic circuit, or it might pull the voltage down too much making the input voltage at the pin remain at a constant logical low value, with no regard to the switch position.

An example is a pull-down resistor used in a digital circuit. A pushbutton switch  is connected between the supply voltage and a microcontroller pin. When the switch is closed, the microcontroller input is at a logical high value, but when the switch is open, the pull-down resistor will pull the input voltage down to ground (logical zero), preventing an undefined state.
Microhm Electronics provide wide range of resistor, like metal resistors, film resistors, foil resistors and more for customers' options.

Keywords:Pull-Up Resi

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