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Can you solve this puzzle?

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thunder3000

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I have been looking at different references about the Chopper Amplifier and all of them mention that the Duty Cycle MUST be 50%.
( see page 27 of www.ewh.ieee.org/tc/sensors/Tutorials/makinwa.pdf)

As far as I can see, as long as the modulator and demodulator both use the same chopping signal, the duty cycle is not important.

My questions:
What will be the influence of changing the duty cycle?
How will this affect the residual offset noise?

Any links or references are very much appreciated.
Thanks!!
 

If the duty cycle was (1% - 99%) then the chopped noise could still pass through the LPF.

BUT... if the difference was like (48% - 52%) then would it still be a problem?
 

Vout = 0.5*(Gain*(Vin-Voff)*D+Gain*(Vin+Voff)*(1-D)),

Where D is duty ratio. If duty ratio is equal to 0.5

Vout=Gain*Vin

so offset is eliminated.
 

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