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Gain and Bandwidth of CMFB in LVDS (Read 407 times)
analog_design
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Gain and Bandwidth of CMFB in LVDS
Nov 22nd, 2012, 5:47am
 
Hi,

How can we decide open loop Gain, Bandwidth as well Loop gain and bandwidth for CMFB circuit in LVDS Transmitter driver .

Please, let me know. I am wondering about it.

Thank You
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raja.cedt
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Re: Gain and Bandwidth of CMFB in LVDS
Reply #1 - Nov 22nd, 2012, 12:27pm
 
hello,
please post the schematic. is it an hbridge with current source or any thing else?

Thanks,
Raj.
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analog_design
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Re: Gain and Bandwidth of CMFB in LVDS
Reply #2 - Nov 22nd, 2012, 10:56pm
 
Hi Raja,

attached is schematic of LVDS Transmitter from Boni paper. I am trouble to define specs for  opamp and CMFB Circuit.

Please let me know.


Warm Regards,
Girish
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LVDS_Tx.jpg

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raja.cedt
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Re: Gain and Bandwidth of CMFB in LVDS
Reply #3 - Nov 23rd, 2012, 4:25pm
 
hello Girish,
i guess it will be tough to define precise gain and BW.

Gain: CMFB gain will decides common mode error, which may impact receiver performance by it's input common mode change. If you have ac coupling at receiver then i guess gain wont impact much. There are few standards which are having tough spec on TX common mode variation, but there will be some min max range.

BW:  For example there if common mode disturbs, then loop should restore back in few bits span otherwise you receiver front end may be effected. This will get you the bandwidth limitation.

Thanks,
Raj.
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