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What is the DC offset and how to measure it?

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Hi all,

Can anyone explain the DC offset concept ? I need a good document on it, when we say DC offset, what is it exactly the main concern ?

How to measure DC offset e.g if i have a sine wave--can i read a DC offset from it, how ?

Thanks in advance !
 

zero if dc offset

dc offest 。。。for receiver ，when LO mixed with itself，（main because some leakage from pll to lna、mixer input for what ever reason like imperfection of isolation or em coupling or reflection），it will create dc offset，

it important that DC offset can be upon some mV level for worst case，which mean if a 80db agc amplifier following the mixer will amplify it to some level beyond 10v（or clamp to your supply），it is just ending to make all the latter circuit saturate。

to measure it ，maybe input the receiver with no signal and watch the output，it is the same with opamp offset，but for different input signal ，the dc level differs
 

Re: DC offset !

If the DC-offset is large , How do you solve it ? Any method ? Thanks
 

Re: DC offset !

it is regarding the opamp .
 

Re: DC offset !

Iif the application is in audio , The BW is zero-IF , How do u do it ?
 

DC offset !

well, i think free DC coding techniques are used
also in TDMA u can use offset cancellation between Bursts but this doesnt remove offset from interferer
 

DC offset !

The solution is a DC compensation loop. There are many papers in IEEE on this issue.
The loop has a certain BW too, so you will have an high pass transfer function with pole(s) at low freq, but you don't need to integrate big capacitors (the one required for ac coupling).
I hope it can help.
Mazz
 

Re: DC offset !

I see many complicated answers above.

consider this expression:

signal(t)= Vdc + Vac*sin(ωt)

Vdc is the "dc offest"


One could see this with a DC coupled oscilloscope.
 

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