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cmos fully differential amp voltage scaling (Read 3632 times)

steven Community Member Offline Posts: 59	cmos fully differential amp voltage scaling Dec 26^th, 2005, 8:42am Hi, I obtained a cmos fully differential folded cascode circuit. The circuit was designed on 2um process. Now the same will be used on 0.18um for a prototype. I wonder if there is a better way to scale the bias voltages in the circuit (Vdd and Vss are still the same as the original circuit). Thanks
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irfan

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Re: cmos fully differential amp voltage scaling
Reply #1 - Jan 8^th, 2006, 3:14pm

In my opinion it is a new design. Sure the architecture is the same, but the 0.18-um process is about at least six or seven generations ahead of the 2-um process. You will have to watch out for the following:

(1) Break down voltages for the 0.18-um process as the supplies from the 2-um design haven't changed
(2) Sure, Vth & Lmin are small now, but watch out for the voltage dependent Rds & gm as both Vth & L_effective have voltage dependency now.
(3) Lower Vth, will also lower your maximum output swing
(4) More leakage current in stand-by mode

That's all I can think of now. The last time I desgined a folded cascode in 0.18-um was back in 2001. If you need more help, I can dig up my old notes. :)

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steven Community Member Offline Posts: 59	Re: cmos fully differential amp voltage scaling Reply #2 - Jan 8^th, 2006, 7:33pm Hello Irfan, What you pointed out is correct. Maybe your notes have something not covered. Anyway, the notes should be helpful. Regards, Steven
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ywguo Community Fellow Offline Posts: 943 Shanghai, PRC	Re: cmos fully differential amp voltage scaling Reply #3 - Jan 10^th, 2006, 3:40am Steven, I guess that the original design (2um) is operater at 5V supply that may destroy a 0.18um circuit eventually. yawei
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steven Community Member Offline Posts: 59	Re: cmos fully differential amp voltage scaling Reply #4 - Jan 10^th, 2006, 10:29am Hello Yawei, This is a good point. So some level shifting may come as an option? I would see how Irfan's design approach. Steven
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zhonghan Junior Member Offline Posts: 16 china	Re: cmos fully differential amp voltage scaling Reply #5 - Jan 15^th, 2006, 8:55pm it is easier to adjust biases for the circiuts than to reduce the power voltage. I am a new comer of the community ,very glad to discuss problems with you.
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