How do I choose a pull-down resistor?

How do I choose a pull-down resistor?

The actual value of the pull-up’s resistance depends on the impedance of the input pin, which is closely related to the pin’s leakage current. A rule of thumb is to use a resistor that is at least 10 times smaller than the value of the input pin impedance.

What is the role of the pulldown resistor pull down any stray voltage to ground Give defined input when the switch is not pressed protect the IC from burning protect the switch?

A pull-up resistor connects unused input pins (AND and NAND gates) to the dc supply voltage, (Vcc) to keep the given input HIGH. A pull-down resistor connects unused input pins (OR and NOR gates) to ground, (0V) to keep the given input LOW.

What is the benefit and role of pull up and pull down resistors in CMOS andin the input and output pins?

A pull-up resistor allow controlled current flow from supply voltage source to the digital input pins, where the pull-down resistors could effectively control current flow from digital pins to the ground. At the same time both resistors, pull-down and pull-up resistors hold the digital state either Low or High.

Why do I need a pull down resistor?

The pull-down resistor must have a larger resistance than the impedance of the logic circuit, or else it might be able to pull the voltage down by too much and the input voltage at the pin would remain at a constant logical low value – regardless of the switch position. The appropriate value for the pull-up resistor is limited by two factors.

How to choose a pull up resistor value-build electronic circuits?

The input impedance of the 555 timer is 10 Megaohms according to electronicsclub.info. And 10 times smaller is 1 MΩ. That gives you the choice of a pull-up resistor value of anywhere in between 5 kΩ and 1 MΩ. So as you can see, you can use a range of values here.

How big of a resistor do I need for a 5V switch?

A rule of thumb is to use a resistor that is at least 10 times smaller than the value of the input pin impedance. In bipolar logic families which operate at operating at 5V, the typical pull-up resistor value is 1-5 kΩ. For switch and resistive sensor applications, the typical pull-up resistor value is 1-10 kΩ.

Why is R1 not a pull up resistor?

Is because it is connected to VCC. But why not R1 is pull resistor ? It is also connected to VCC It’s because of its purpose. R2 is there to “pull up” the voltage when the button is not pushed. That is not the purpose of R1.