Drain to bulk capacitance calculations analytically

My question is in equation: Cdb = Keqn . ADn . Cj + Keqswn . PDn . Cjsw, where do we find (SPICE model?)/how can we calculate the values of Keqn and Keqswn? Cheers.

by Ams0
November 20, 2017

Looking at http://index-of.co.uk/Electronics/Jan_M._Rabaey-Digital_Integrated_Circuits-Prentice_Hall(1995).pdf, it would appear that reasonable values are given in chapter 5, example 5.3

by mikerogerswsm
November 20, 2017

In op. cit. Ch 3 section 3.3.5 (p118) the SPICE models are commented on. Earlier on p114 values are given for capacitances, these are for a particular 0.25um process and should be scaled accordingly.

by mikerogerswsm
November 20, 2017

Please bear in mind that all these numbers are at best good guesses dependent on process measurements and that they have scatter from day to (production) day and vary with temperature and supply voltage. Back in my CMOS days nearly forty years ago we were far less worried about the details, and just used ball-park figures. SPICE was then in its infancy and to be used with caution, we knew of errors.

by mikerogerswsm
November 20, 2017

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