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What is the use of bias resistor?

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kumecepent

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Dear Friends,

What is the use of bias resistor? Is it really helpful to reduce the noise or ripple in DC signals?

FYI, I have a good amount of noise with ripple in a DC square wave signal with 2KHZ @ 5V amplitude. After connecting a resistor across +ve terminal of measurement terminal with reference to AI ground and also -ve terminal with reference to AI ground.

Could you explain the effect behind this...what...how...?
 

Re: Use of Bias resistor

Bias means putting some standing current or voltage across/into some device to improve it's performance.
Did you mean that putting a resistor across your measurement terminals the noise went down? As you mention ripple and noise, I guess you are using an oscilloscope, or how do you know what the signal consists off? All measurements are two terminal, normally one is "common, or earth". The input impedance of an oscilloscope is at least 1M ohm, so it will pick up radiated signal from the mains hum to the local radio station, especially if the leads to it are long and unscreened. Putting a resistor in parallel will reduce the input impedance so the effects of pick up are reduced, BUT you are loading your circuit, which may be unable to supply the correct voltage into a low value resistor.
Frank
 

Re: Use of Bias resistor

Dear chuckey,

Thanx for ur reply. It was really helpful. Expect the same for the details below.

Yes,the ripple was reduced by that bias resistor.

No it's not an oscilloscope. I'm using a Data Acquisition card. It has 16 bit resolution. (NI 6221).

Can i connect a higher range of resistor 10K or more across +ve terminal and ground to remove the noise. If yes, what is the purpose? how it works?
 

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