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 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_nC_ox(W/L) = 10^-4 Amp/V², 

                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 10¹⁸/cm³

(b)   W_E  =  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 τ_n = 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.