Tuesday, 11 June 2013

Video Solutions for GATE 1997 ECE : Five Mark Questions ( Electron Devices )

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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