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Oct 17th, 2019, 4:07pm
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calculation of total width of MOS using finger width and multiplier (Read 1039 times)
Sagar Juneja
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calculation of total width of MOS using finger width and multiplier
Jan 18th, 2018, 2:42am
 
If we are given a finger width, numbers of fingers and multiplier then as per my understanding the total width of MOS = finger_width*number_of_fingers*multiplier.

Is my understanding correct? I refereed  to one sample circuit in cadence manual, i am not been able to understand how they have calculated the total width. Screenshot is attached.
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Andrew Beckett
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Re: calculation of total width of MOS using finger width and multiplier
Reply #1 - Jan 21st, 2018, 8:26am
 
The example is not a particularly great one because it's inconsistent. The database is from the SpectreRF workshop which is in <SPECTREinstDir>/tools/spectre/examples/SpectreRF_workshop/rfworkshop.tar.Z and looking at the CDF for this component, it seems that most of the parameters are not used - it's only the length, the multiplier, and the number of fingers that are netlisted for these RF transistors. The width is defined in the model as 1.5u. The other parameters which are displayed in the edit properties form are not consistent - there are no callbacks to compute them.

So don't get too hung up on this specific example - it's not intended to be a real life PDK - it's an example which has been adapted a few times and is not representative of a real-life design kit.

Regards,

Andrew.
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Tako
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Re: calculation of total width of MOS using finger width and multiplier
Reply #2 - Jan 23rd, 2018, 5:22am
 
Generally speaking this formula:

total width of MOS = finger_width*number_of_fingers*multiplier

is a proper one. But keep in mind that 1um x 4 x 5 (W x F x M) transistor would behave a little differently than 2.5um x 2 x 4 transistor .
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