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[SOLVED] fully differential amplifier realization based on two single ended amplifiers

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user0088

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How to implement fully differential amplifier based on two single ended amplifiers.



Thanks.
 

Dear user0088
Hi
Say your mean more accurately , please.
Regards
Goldsmith
 

user0088 said:
How to implement fully differential amplifier based on two single ended amplifiers.
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Cross-connect the inputs (INP1=INN2 , INN1=INP2) , VREF1=VREF2 . Standard feedback.
 

Cross-connect the inputs (INP1=INN2 , INN1=INP2) , VREF1=VREF2 . Standard feedback.
Click to expand...
You'll need an additional common mode feedback path to implement a fully differential amplifier. Otherwise the "standard feedback" isn't able to keep both outputs within reasonable bounds.
 
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FvM said:
You'll need an additional common mode feedback path to implement a fully differential amplifier. Otherwise the "standard feedback" isn't able to keep both outputs within reasonable bounds.
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erikl and FvM, thanks a lot for your replies.
How to implement your mentioned "additional common mode feedback path" ? Could you please show any example.

Thanks.
 

You'll find a detailed discussion of fully differential amp CMFB in text books, e.. Gray, Hurst, Lewis, Meyer Analysis and Design of Analog Integrated Circuits and in some amplifier datasheets, e.g. the below block schematic from TI. I assume, you should be able to figure out the purpose of CMFB when thinking about it a bit.

 
erikl and FvM, thanks a lot.
 

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