UNIVERSITY OF CALIFORNIA AT BERKELEY College of Engineering Department of Electrical Engineering and Computer Sciences Course Review EE 105 Prof Liu Fall 2007 The following notes might be useful as a review for the final exam This is not a comprehensive review but it covers the key concepts that were discussed this semester Semiconductor Physics Intrinsic carrier concentration at 300 K ni 1010 cm 3 Mass action law at thermal equilibrium n0p0 ni2 Doping ni2 o n type n0 N d N a and p0 Nd Na ni2 o p type p0 N a N d and n0 Na Nd Drift current current due to movement of charged particles in an electric field Diffusion current movement of charge carriers from high conc to low conc J drift J n drift J p drift q n n0 p p0 E E dn dp J diff J n diff J p diff q Dn Dp dx dx D kT Einstein s relation q Resistivity o Conductivity n0 q n p 0 q p 1 o Resistivity o Resistance R 1 n0 q n p 0 q p L L RS where RS is the sheet resistance tW W pn Junctions Depletion region o Region of immobile ions at junction o Depletion region edge on n side x n 0 2 s bi qN d Na Na Nd o Depletion region edge on p side x p 0 2 s bi qN a Nd Na Nd o Depletion width x d 0 x n 0 x p 0 Charge density Electric field solve using Gauss Law Potential profile 2 s bi qN d 1 1 Na Nd dE 0 0 x dx S Nd kT where Vth ni q n o Potential on p side outside depletion region p Vth ln i Na o Built in potential bi n p o Potential on n side outside depletion region n Vth ln Reverse bias depletion region width electric field in junction o o Depletion width X d V D X d 0 1 Junction capacitance C j C j0 1 VD VD bi where VD is the reverse bias voltage where C j 0 q s 2 bi Na Nd Na Nd bi IV curve for pn junction Note breakdown occurs under a large reverse bias MOSFETs nMOS Structure BJTs npn Structure MOSFET IV curve BJT IV curve MOSFET drain current saturation ID 1 W n C ox VGS VTn 2 1 VDS VDsat 2 L Transconductance and ro BJT currents I C I S exp IB 1 IC VBE VT W VGS VTn L W g m 2 n C ox ID L 2I D gm VGS VTn 1 ro I D g m n C ox I E IC I B Transconductance and ro VT IC V ro A IC gm Large signal models Forwardactive Large signal models Saturation Small signal model Small signal model Single Stage Amplifiers MOSFETs nMOS Common source BJTs npn Common emitter Av g m RC ro Rin r Rout RC ro Common source with degeneration Common emitter with degeneration Rin r 1 R E R B Rout RC ro Common base Common gate Av g m RC 1 1 R E g m r r R B Rin RE 1 g m r RB r Rout RC ro Common drain source follower Common collector emitter follower Rin r 1 R E Rout RE 1 ro gm Multistage Amplifiers Cascode Current mirror Current mirrors formed by MREF MI1 and by MREF MI2 W L 1 I1 I REF W L REF and W L 2 I2 I REF W L REF Differential pair Minimum common mode output voltage Frequency Response Bode plots Transfer function Magnitude rises with slope of 20 dB dec after a zero is reached Magnitude falls with slope of 20 dB dec after a pole is reached Example Bode plot Miller s Theorem use to approximate floating capacitors Intrinsic MOSFET capacitances
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