Subthreshold Operation and gm/Id design - CppSim

PerrottAnalysis and design of Analog Integrated CircuitsLecture 16 Subthreshold Operation and gm/IdDesignMichael H. PerrottApril 1, 2012 Copyright 2012 by Michael H. PerrottAll rights PerrottA Closer Look at Transconductance Assuming device is in strong inversion and in saturation:2 IdVgsId_op VVTHVgs_opVds > VM1 IdVgsNMOS gsdgm = Vgs IdVgs_opID= nCox2WL(Vgs VTH)2(1 + Vds) gm= Id Vgs nCoxWL(Vgs VTH) s2 nCoxWLId gm Idq2 nCoxW/L Id 2Id(Vgs VTH) PerrottUnity Gain Frequency for Current Gain, ft Under fairly general conditions, we calculate: ftis a key parameter for characterizing the achievable gain bandwidth product with circuits that use the device3|Id/Iin| PerrottCurrent Density as a Key Parameter Current density is defined as the ratio Id/W.

M.H. Perrott Key Insights Related to Current Density Current density sets the device operating mode-Weak inversion (subthreshold): highest gm efficiency- Achieves highest gm for a given amount of current, I d Strong inversion: highest f t- Achieves highest speed for a given amount of current, I dModerate inversion: compromise between the two ...

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  Operations, Design, Cppsim, Subthreshold, Subthreshold operation and gm id design cppsim

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