How to decide the width of transistors for detector design?

[karthik167]

Transistor sizing

Hi,

I need to design a Phase-Frequency detector for my course project. After searching the literature I have decided upon the transistor level schematic I am going to use. But I am not sure how to decide the width of each transistor? Can someone please show me the start point in attacking this problem. I am not sure where to start?

Thanks,
Karthik

PS: I would be using cadence for my simulation.

 

[nemolee]

Re: Transistor sizing

I give you one web site for your reference.
**broken link removed**

 

[karthik167]

Re: Transistor sizing

neeolee,

thanks for the link, but my question is different. I would be using a dynamic logic PFD and I would like to know how to decide the size of different transistor to optimize speed/area/power.

 

[amarnath]

Transistor sizing

u cannot be sizing the transistors for all the three area power and speed in the first case.u need to get ur specs right.then if u want greater speed,then size them more than minimal.be careful cause u can do this only until delay is not dominated by the intrinsic capacitance of the transistor.once intrinsic capacitance starts to dominate,then incereasing size of the transistors will lead to greater delay.now u can see the trade off that when u are increasing transistor sizes,it is leading to an increase in area.now coming to low power, u need to minimise the capacitance at the output node,which can be done by using minimal transistor sizes where ever required.so again u can see a trade off between speed and power.so just keep these things in mind,before anything.

regards
amarnath