Download Carrier Concentrations - Microelectronic Devices and Circuits - Exam and more Exams Microeconomics in PDF only on Docsity! EECS 105, Fall 1993 Midterm #2 Professor R. T. Howe Ground Rules: Closed book and notes; one formula sheet (both sides)• Do all work on exam pages• Answers accurate to within 10% will receive full credit• Default bipolar transistoe parameters: npn: (beta)n = 100, VAn = 50 V, ISn = 10 -16 A. pnp: (beta)p = 50, VAp = 25 V, ISp = 10 -16 A. • Default MOS transistor parameters: NMOS: (mu)n C ox = 50 (mu)AV-2, (lambda)n = 0.02V-1, VTn = 1 V. PMOS: (mu)p C ox = 25 (mu)AV-2, (lambda)p = 0.02V-1, VTp = -1 V. • Problem #1. Matched Complementary Bipolar Transistor Design [12 points] The cross sections, minority carrier concentrations, and circuit schematics are shown for matched npn and pnp vertical BJTs, operated in the forward-active region. EECS 105, Midterm #2, Fall 1993 EECS 105, Fall 1993 Midterm #2 Professor R. T. Howe 1 Given: all doping levels are matched and the emitter areas are identical NdE (npn) = NaE (pnp)• NaB (npn) = NdB (pnp)• NdC (npn) = NaC (pnp)• AE (npn) = AE (pnp)• Given: the bias volatages for the two transistors are matched and both are in the forward-active region VBEn = VEBp• VCEn = VECp• (a) [5 pts.] In order for the npn and the pnp transistors to have matched collector currents, ICn = | ICp |, determine the numerical value of the base width of the pnp, WBp. Given: the base width of the npn is WBn = 0.2 (mu)m, the electron diffusion coefficient (diffusivity) is Dn = 20 cm2s-1, and the hole diffusivity is Dp = 10 cm2s-1 -- these are valid for the emitter, base, and collector of each transistor. (b) [5 pts.] In order for the npn and the pnp transistors to matched base currents, IBbn = | IBp |, determine the numerical value of the emitter width of the pnp, WEp. This part is independent of part (a). Given: the emitter width of the npn is WEn = 0.1 (mu)m, and Dn = 20 cm2s-1, Dp = 10 cm2s-1. (c) [2 pts.] Which transistor has the smaller Early voltage, VA? Explain why in one sentence. EECS 105, Midterm #2, Fall 1993 Problem #1. Matched Complementary Bipolar Transistor Design [12 points] 2
