EE105 Fall 2005 Microelectronic Devices and Circuits Lecture 13 Two Port Models Common Source Amplifiers Revisited Announcements Homework 6 due today No labs this week Lab 5 next week Reading Chapters 9 4 8 MOS only Midterm 1 on Thursday October 13 6 30 8pm Sibley Review session today October 11 6 30 8pm 277 Cory No office hour next Monday Please come and see me after the lecture on Tuesday 2 1 Lecture Material Last lecture MOS current sources This lecture Generalized two port models Common source amplifier again 3 Maximize Gain of CS Amp Av g m RD ro Increase gm more current Increase RD free Don t need to dissipate extra power Limit Must keep the device in saturation VDS VDD I D RD VDS sat For a fixed current the load resistor can only be chosen so large To have good swing we d also like to avoid getting to close to saturation 25 2 Current Source Supply Solution Use a current source Current independent of voltage for ideal source 26 CS Amp with Current Source Supply 27 3 Load Line for DC Biasing Both the I source and the transistor are idealized for DC bias analysis 28 Two Port Parameters From current source supply Rin Gm g m Rout ro roc 29 4 P Channel CS Amplifier DC bias VSG VDD VBIAS sets drain current IDp ISUP 30 Two Port Model Parameters Small signal model for PMOS and for rest of circuit 31 5
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