1.The current I in a forward biased P

_{+}N junction shown in
figure (a) is entirely due to diffusion of holes from x=0 to x=L.

The
injected hole concentration distribution in the n- region

is linear as shown in
figure (b), with P(0) = 10

^{22}/cm^{3}and
L = 10

^{-3}cm. Determine :
(a) The current density
in the diode assuming that the diffusion

coefficient of holes is 12 cm

^{2}/sec.
(b) The velocity of holes in the n-region at x=0.

2. It is required to use a JFET of figure as linear resistor.

The parameters of the JFET are as follows:

W = 100 µm, L =
µm,
a = 2.5 µm.

The doping in the n-layer is N

_{D}= 10^{16}/cm^{3}and
the electron mobility is 1500 cm

^{2}/V-sec. The depletion layer
width of each junction due to the built in potential is 0.25 µm.

The two P

^{+}gate regions are connected together externally.
The
resistances of the regions outside the gate are negligible.

Determine the
minimum value of the linear resistor which can be

realized using this JFET
without forward biasing the gate

junctions.

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