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which transistor to use (Read 1504 times)

ontheverge

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which transistor to use
Nov 24^th, 2010, 8:20pm

Hi,

there are a number of choices for MOS transistor in tsmc0.18um process, categorized into rf devices and logic devices.

if I'm to design ADC at 10MS/s conversion rate, which type of transistor should I choose, (what about 50MS/s, what is the criteria?)

For logic devices, it comes with varying Vts, again, what is the criteria for choosing them, i guess it's easy to say that it depends on target speed and power, but can anyone explain in more detail?

thanks,
Steve

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ywguo

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Shanghai, PRC

Re: which transistor to use
Reply #1 - Nov 26^th, 2010, 2:40am

Hi Steve,

Usually the RF transistors are characterized for radio frequency application, where the parasitic cap/res impact the performance. And it has bigger layout area because those RF transistors has guard ring in the layout. So please don't use RF transistors when you design ADC operating at 10MS/s or 50MS/s. I assume you design a nyquist rate ADC.

As of the multiple threshold voltage of MOS, you'd better to use MOS with normal Vth to reduce cost. However, you may use lvt or hvt MOS for high performance or easy design if your boss does not prohibit you from using lvt and hvt MOS.

Best Regards,
Yawei

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