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Output impedance vary with VDS ?

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manish12

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I am making the analog mixer for rf range 2.2GHz.
In some ieee paper I reads probs in rf range in that a point is there which say that Z0 Vs Vds.
If it is so what should be the design strategy for mixer / any circuit in rf range.
Does it make any serious prob ?
 

Hello,

Variations of Zo with Vds results from the fact that the circuit parameter varies with vds. If you are designing under matching condition, i.e the output impedence must be 50Ω etc, these variatios are harmul. you need to make your design more immune to supply variations.This would be the case if your mixer is driving an off chip filter.
On the other hand, if the mixer is to drive another on chip stage you will only need make sure these variations dont effect next stage.[/b]
 

The o/p impedance does vary with with Vds ( because of CLM). Try to increase the channel length to 3x of min channel length of the technology. This will make the lambda lesser (lambda is inversely proportional to channel length). Lesser the lambda, lesser the variation due to Vds. I understand that there is trade off in frequency to device dimension. As larger the device dimension, more the parasitic capacitance which will reduce the bandwidth.

In addition keeping the device in deep saturation will also help in making the o/p impedance higher.



manish12 said:
I am making the analog mixer for rf range 2.2GHz.
In some ieee paper I reads probs in rf range in that a point is there which say that Z0 Vs Vds.
If it is so what should be the design strategy for mixer / any circuit in rf range.
Does it make any serious prob ?
Click to expand...
 

supply may varies the z0 it is the conclution . thats it .
and it may create some problems.
 

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