h08_lecture5_2

h08_lecture5_2 - EE 214 Lecture 5 (HO#8) B. Murmann 1...

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Unformatted text preview: EE 214 Lecture 5 (HO#8) B. Murmann 1 Lecture 5 EE214 Technology: f T and Intrinsic Gain g m /I D Design Methodology Boris Murmann Stanford University murmann@stanford.edu Copyright 2004 by Boris Murmann EE 214 Lecture 5 (HO#8) B. Murmann 2 Overview Reference F. Silveira et. al. "A g m /I D based methodology for the design of CMOS analog circuits and its application to the synthesis of a silicon-on-insulator micropower OTA," IEEE Journal of Solid-State Circuits , Sept. 1996, pp. 1314-1319. Introduction Today, we'll continue to characterize the EE214 technology. The two remaining figures of merit that are of interest to us as circuit designers are f T and intrinsic device gain. In conclusion, we find that V OV is not "directly" related to either performance metric we care about. Hence, we switch towards a strategy called "g m /I D design methodology", in which g m /I D , rather than V OV is used directly as a central design variable. EE 214 Lecture 5 (HO#8) B. Murmann 3 Performance Metrics of Interest Transit Frequency gs m T C g = Transconductor Efficiency D m I g Intrinsic Gain o m r g EE 214 Lecture 5 (HO#8) B. Murmann 4 f T Simulation $ ft vs. gate overdrive $ Boris Murmann, September 2004 .param gs=1 vgs g 0 dc 'gs' mn1 g g 0 0 nch214 L=0.35um W=10um .op .dc gs 0.4V 1.2V 10mV .probe ov = par('gs-vth(mn1)') .probe ft = par('1/2/3.142*gmo(mn1)/(-cgsbo(mn1))') .options post brief dccap .lib './ee214_hspice.txt' nominal .end 10/0.35 EE 214 Lecture 5 (HO#8) B. Murmann 5 Result 2 2 1 L V f OV T = Long Channel:-0.2-0.1 0.1 0.2 0.3 0.4 0.5 5 10 15 20 25 30 NMOS W/L=10/0.35 V OV [V] f T [GHz] EE214 technology Long Channel Fit EE 214 Lecture 5 (HO#8) B. Murmann 6 Observations - f T Again, a simple long channel model doesn't do a very good job Large f T discrepancy in weak inversion and in strong inversion, at large V OV The reasons for these discrepancies are exactly the same as the ones we came across when looking at g m /I D Bipolar action in weak and moderate inversion...
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This note was uploaded on 04/17/2008 for the course EE 214 taught by Professor Murmann,b during the Fall '04 term at Stanford.

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h08_lecture5_2 - EE 214 Lecture 5 (HO#8) B. Murmann 1...

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