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Why does reducing frequency allow for downsizing of transisitors

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rahdirs

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Why does reducing frequency allow for downsizing of transisitors (Weste & Harris)

Hi,

I've recently started reading CMOS VLSI Design by Weste & Harris. While reading, I've found this statement " Reducing frequency allows for downsizing transistors/ using a lower supply voltage, which has an even greater impact on power ".

Why does reducing frequency allow downsizing ? Is it because as you reduce frequency, you can operate with more delay & hence can reduce the width of transistors ? And as you reduce the size of transistors, you can use a lower Vdd with not much change in charging & discharging times ? Am I correct in my reasoning or is there a different reason ?

Regards,
rahdirs
 
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What happens at high frequencies? A transistor must work harder to quickly charge and discharge stray capacitance and its own capacitance. It gets hot when it works hard so it must be large enough to dissipate the heat and a higher supply voltage allows it to work harder. At lower frequencies then the capacitance has little effect.
 

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