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PSpice Reference Guide Analog devices Ir = recombination current = ISR·(e Vgd/(NR·Vt)-1) Kg = generation factor = ((1-Vgd/PB)2+0.005)M/2 Ii = impact ionization current for forward saturation region: 0 < Vgs-VTO < Vds then: Ii = Idrain·ALPHA·vdif·e -VK/vdif where vdif = Vds - (Vgs-VTO) else: Ii = 0 Id = drain current = area·(Idrain-Igd) Is = source current = area·(-Idrain-Igs) All levels: Idrain Normal mode: Vds ≥ 0 Case 1 for cutoff region: Vgs-VTO ≤ 0 then Idrain = 0 Case 2 for linear region: Vds < Vgs-VTO then: Idrain = BETA·(1+LAMBDA·Vds)·Vds·(2·(Vgs-VTO)-Vds) Case 3 for saturation region: 0 < Vgs-VTO < Vds then: Idrain = BETA·(1+LAMBDA·Vds)·(Vgs-VTO)2 Inverted mode: Vds < 0 Switch the source and drain in the normal mode equations above. JFET equations for capacitance All capacitances are between terminals of the intrinsic JFET (that is, to the inside of the ohmic drain and source resistances). Gate-source depletion capacitance June 2007 194 Product Version 16.0
