pipelind ADC bias circuit

[ljy4468]

hello?

I've a question about bias circuit.
I'm using 1.5bit per stage structure.
So, there are one amp per one stage...

Can I use one bias circuit for all amp?
or one bias circuit for each amp?

Thanks in advance.

 

[Syukri]

Basically u can just use one bias circuit for all op-amp...

But it's better if every op_amp got their own biasing circuit becase in pipiline adc their are using two phase non-ovelaping clock where in one main clock two stage is working.

 

[ljy4468]

Thanks your answer, Syukri!
But I don't understand correctly.
There are non-overlapping clock, then why using own biasing circuit is better????
Please tell me more
Thanks

 

[ezt]

Hi ljy4468,
I think if all of your 1.5-bit stages are the same, there is no problem with using the same bias circuit for all of them. But if you use scaling (especially error scaling) in stages, i.e. each stage may have more error than the previous stage, then maybe bias voltages would differ from eachother in different stages and using different bias circuits is mandatory.
However I think using the same bias for all stages may result in layout to be unbalanced (all stages that should be the same are not exactly the same!). But if this happens in last stages there is no problem due to their less importance.

Regards,
EZT

 

[opamp741]

In transients each stage will cause some distrubance in the bias circuit (voltages).
the bias sharing sometimes causes loops at system levels and u have to
be very careful abt stability of that loop.

 

[ljy4468]

oh...I understood.
Really thanks all!!!