GEORGIA INSTITUTE OF TECHNOLOGY
School of Electrical and Computer Engineering
ECE3040B
Microelectronic Devices and Circuits
Spring 2000
Final Exam
2 hour 30 min
Problem 1. (40Pts)
A 1mm long silicon rod has a rectangular cross section of 4µm×10µm. The rod is uniformly
doped p-type at T=300K with NA=5×1017 cm-3 and ni(Si)=1010 cm-3 . A voltage potential of 5V is
applied across the two ends of the rod.
a) Calculate the current passing through the rod due to this electrostatic potential.
b) Is the current calculated in part (a) a drift current or diffusion current? Is it mainly due to
holes or electrons?
c) This silicon sample is compensated by adding ND=5×1017 cm-3 donors.
conductivity of the compensated sample.
Calculate the
d) We also have an intrinsic silicon rod (identical in dimensions to the first rod) that we
would like to dope it n-type to a level that the resistance of the doped rod is maximum.
Assuming that the electron and hole mobility’s are constant, and µn /µp =2.5, find out the
required doping level.
Problem 2. (40Pts)
Derive and draw the voltage transfer characteristics for the circuit shown below. Assume that
diodes are ideal (Von =0) and +15≥Vs≥-15. Label on your plots the slop of all lines, the
coordinates of all break points, and the state of each diode in each region.
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Problem 3. (25Pts)
For the BJT amplifier shown below, (a) find the Q-point of the transistor assuming β=50 and
VA=50V. (b) What are AV, AI, RIN, and ROUT for this amplifier?
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