the problems are in the attachment
Problem 1:
In this problem you will design a BJT to achieve a punch through voltage V CE greater than 6 V.
The emitter, base, and collector doping levels of the BJT are given as
N E=2×1019
cm
−3
, N B=4×1017
cm
−3
and NC=6×1016
cm
−3
,respectively.ni=1010
cm
−3
,
kT
q
=0.026V
What is the required minimum metallurgical base width W BM such that the punch through voltage
V CE (PT ) is greater than 6V ( V CE=V CB+V BE ). Assume operation in active mode with
V BE = 0.75 V. Due to emitter high doping, band gap narrowing of 0.09 eV occurs in emitter region
which also reduces the base-emitter built-in voltage. For depletion widths x pBE , x pBC at the
base-emitter and base-collector junctions, respectively, and neutral base width W B
, the
metallurgical junction width W BM is defined as:
W BM =W B+x pBE+x pBC
a) What is the BJT neutral base width at punch-through ?
b) What is the effective built-in voltage at base-emitter junction?
c) Calculate the depletion layer width x pBE
d) What is the built-in voltage at base-collector junction?
e) What is the voltage V CB at punch-through?
f) Calculate the depletion layer width x pBC
g) The metallurgical base width?
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