Diodes for Signal ProcessingDiodes for Signal ProcessingEE122D. W. ParentD. W. Parent1Diodes can be used for more than just rectification.•Light emitting diodesLight emitting diodes• Laser diodesSl Cll•Solar Cells• Signal Processing)1(eIIVVT−×=ηThis is a lot of floating point operations.1)1(432xxxeIIxs++++−×=This is a lot of floating point operations.I count 17!2.....24621xex++++=Log amplifierLog amplifier⎟⎟⎠⎞⎜⎜⎝⎛−=RIVVVinToutln⎟⎠⎜⎝RIsToutThere are 4 DC spice parameters fdidfor a diode IS Saturation current (Given in Amps)GMIN is a small N Emission Coefficient (No Units)RS Parasitic resistance (Given in Ω)BV Breakdown Voltage (Given in Volts)IBV Breakdown Current (Given in Amps)resistanceTo prevent a value of zero current formFlowing Usually setIBV Breakdown Current (Given in Amps)Flowing. Usually set to 10-12S4Full Diode ResponseFull Diode Response5Test the diode of a NMOSTest the diode of a NMOS6Note there are two diodes being tested.Forward Bias DiodeLiLinear1.20E+011.40E+011.60E+016.00E+008.00E+001.00E+01VD(V)Series10.00E+002.00E+004.00E+000.00E+00 2.00E-01 4.00E-01 6.00E-01 8.00E-01 1.00E+00 1.20E+00ID(A)7Take the RS value from the Linear fh didpart of the diode curvey = 77 327x 62 4721.60E+011.60E+01y = 77.327x - 62.472R2 = 11.00E+011.20E+011.40E+018.00E+001.00E+011.20E+011.40E+01D(V)2.00E+004.00E+006.00E+008.00E+00000E+002.00E+004.00E+006.00E+00VD0.00E+000.82 0.84 0.86 0.88 0.90 0.92 0.94 0.96 0.98 1.00 1.020.00E+000.00E+00 2.00E-01 4.00E-01 6.00E-01 8.00E-01 1.00E+00 1.20E+00ID(A)8Forward Bias Ln Scale(RS i i i d)(RS position omitted)1.40E+011.60E+014.00E+006.00E+008.00E+001.00E+011.20E+01VD(V)0.00E+002.00E+000.00E+00 2.00E-01 4.00E-01 6.00E-01 8.00E-01 1.00E+00 1.20E+00ID(A)0y = 38.664x - 31.543R2 = 1-10-50.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80Do not use linearRegion of DiodeOr too close to 0V.-20-15The RS value and GMINWill skew the results.9-30-25Behavioral DC models are easy to create.10Series Resistance Dominates at higher voltages.Slope should equal 1/RsSlope=.947 s11To see exponential function plot log.Rs starts to dominate performance1≤TVVeηperformance.This is the valid range for il i1TVVηsignal processing.1>>TVeη12Do not use 10 based log to extract Is and n!!!!Extract IS and n fromln(I)!Extract IS and n from ln(I)!bSeI =mVn1=91.8.20===−nAeeIbSTmV996.02590759381=×=nS0259.0759.38×8200645756938296718−=×−−=−=mxyb138.200645.7569.382967.1811−=×−−=−=mxybReplace Set up with “real”
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