1. In the cascade amplifier circuit shown, determine the values

of R

_{1}, R_{2}and R_{L}such that the quiescent current through the
transistors is 1 mA and the collector voltages are V

_{C1}= 3 volts,
and V

_{C2}= 6 volts. Take V_{BE}= 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 :

V

_{DD}= 10 volts, β = µ_{n}C_{ox}(W/L) = 10^{-4}Amp/V^{2},
V

_{T}= 1 volt, and I_{DS}= 0.5 mA.
Evaluate
V

_{DS}and R_{D}. 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)
W

_{C}= 20 µm and collector doping = 5 x 10^{18}/cm^{3}
(b)
W

_{E}= 1 µm and emitter doping = 10 x 10^{19}/cm^{3}
(c)
Base doping
= 5 x 10

^{15}/cm^{3}
(d)
Minority carrier life time in the Base region is
τ

_{n}= 5 µsec
5. An n-type silicon bar is doped uniformly by phosphorous
atoms

to a concentration 4.5 x 10

^{13}/cm^{3}.
The bar has cross section of 1 mm

^{2}and length of 10 cm.
It is illuminated uniformly for region x<0 as shown in figure.

Assume
optical generation rate 10

^{21}electron-hole pairs per cm^{3}
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.

## No comments:

## Post a comment