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Design >> Analog Design >> [help] dc offset cancellation techniques
https://designers-guide.org/forum/YaBB.pl?num=1260267282

Message started by trashbox on Dec 8^th, 2009, 2:14am

Title: [help] dc offset cancellation techniques
Post by trashbox on Dec 8^th, 2009, 2:14am

Hi all,

As attachment, the class-AB driver output is audio signal (20~20KHz) and has 1~10mV DC offset. Is there any method or close-loop DC offset cancellation circuit to eliminated it(spec. require the dc offset <2mV)? Can the so-called servo circuit solve this problem in this case? Thanks in advance.

Regards

Title: Re: [help] dc offset cancellation techniques
Post by duncandu on Dec 8^th, 2009, 1:40pm

Like auto-zero, or servo DAC, etc.
Many techniques on offset cancellation can be applied in this case.

Title: Re: [help] dc offset cancellation techniques
Post by trashbox on Dec 8^th, 2009, 5:56pm

Hi duncandu,
Thanks for your reply. Would you please offer me the servo DAC references?

Best regards

Title: Re: [help] dc offset cancellation techniques
Post by thechopper on Dec 8^th, 2009, 6:32pm

Hi Trashbox,

Check this thread for references on choppers for SE amplifiers...

http://www.designers-guide.org/Forum/YaBB.pl?num=1259664512

Best
Tosei

Title: Re: [help] dc offset cancellation techniques
Post by RobG on Dec 14^th, 2009, 5:05pm

I'm not sure why you are seeing such offset in simulation - are you sure it isn't a finite gain issue? At any rate, if you are using a process 0.5u or smaller you should easily be able to get the offset down by using larger devices. You probably want low 1/f anyway. Chopping might also work well since the input frequency is low, and the ear is a great filter above 20kHz