Can you solve this puzzle?

[thunder3000]

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!!

 

[thunder3000]

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?

 

[Fom]

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.