1. In the cascade amplifier circuit shown, determine the values
of R1, R2 and RL such that the quiescent
current through the
transistors is 1 mA and the collector voltages are VC1
= 3 volts,
and VC2 = 6 volts. Take VBE = 0.7 volts and
assume β
of the
transistors is high and base currents to be negligible.

2. Given an NMOS circuit as shown. The specifications of the
circuit are :
VDD
= 10 volts, β
= µnCox(W/L)
= 10-4 Amp/V2,
VT = 1 volt, and IDS
= 0.5 mA.
Evaluate
VDS and RD. Neglect body effect.

3. Find static noise margins for a BJT inverter shown in
figure.
Transistor used is an npn type with specifications as follows.

4. For a typical n-p-n transistor, the following data are available :
(a)
WC = 20 µm
and collector doping = 5 x 1018/cm3
(b)
WE = 1 µm and emitter doping = 10 x
1019/cm3
(c)
Base doping
= 5 x 1015 /cm3
(d)
Minority carrier life time in the Base region is
τn
= 5 µsec

5. An n-type silicon bar is doped uniformly by phosphorous
atoms
to a concentration 4.5 x 1013/cm3.
The bar has cross section of 1 mm2 and length of
10 cm.
It is illuminated uniformly for region x<0 as shown in figure.
Assume
optical generation rate 1021 electron-hole pairs per cm3
per second, for this case.
The hole lifetime and electron lifetime are equal to
1µsec.
Evaluate the hole and electron diffusion current s at x =
34.6 µm.

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