Pull-up and Pull-down resistor

[yuhiub90]

Can someone tell me what's exactly pull-up and pull-down resistors. I're read a lot but it's not clear enough.
Thanks.

 

[maulin sheth]

Pull up and pull down resistors is same as pull up and pull down transistors in CMOS. pMOS as pull up and nMOS as pull down.

 

[yuhiub90]

Pull up and pull down resistors is same as pull up and pull down transistors in CMOS. pMOS as pull up and nMOS as pull down.

Thanks. So what's exactly their usages?

 

[maulin sheth]

Now we mostly use CMOS technology because of negligible static power consumption and less area required. pMOS is basically used for pull-up means pulling up the output,so whenever pMOS is on the output is 1 in CMOS and nMOS is for pull down means it is used to pull down the output so,whn nMOS is on the output is zero.

 

[yuhiub90]

I think the main use of pull-up and pull-down resistors is to stabilize the input logic level to the logic gate.

 

[maulin sheth]

What you want to say, I can't understand. pl tell clear cut. How can u stabilize the input through Pull up and pull down?

 

[yuhiub90]

**broken link removed**
Take a look at this

 

[ud23]

https://www.edaboard.com/threads/253721/

 

[cheeta@india]

let us say that node is connected to pull down resister.
now what for this resister is used and why is this called pull down resister is question.
So, purpose of using this resister is to pull the node to logic low level when ever that node is floating .
similar is the case with pull up resister.

pull down resister: connect other end of resister to gnd (low logic)
pull up resister : connect other end of resister to VDD(logic high)

 

[subhash_chevella]

Hi,

In simple terms,
Pull down/up are the terms used w.r.t the output node.

ie,
for example consider an Inverter.
in this, depending upon the input logic, the output node voltage is pulled down to GND through NMOS resistor & pulled up to Vdd through PMOS resistor.
In this example NMOS resistor is called Pull Down resistor & PMOS resistor is called Pulled Up resistor.

Similary for all the remaining gates.

regards,
Subhash C