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Phosphorous is doped in a silicon wafer. The impurity concentration is 10^{13}\text{ per cm}^3. If all the donors are active calculate its resistivity at room temperature. The mobility of electrons is 1250\text{ cm}^2/\text{V-s}.
How is frequency modulation advantageous compared to amplitude modulation? Still, why are the video signals transmitted by television stations amplitude modulated?
What is Meissner effect? Superconducting tin has a critical temperature of 3.7 K in zero magnetic field and critical field at 0 K is 306 gauss. Determine the critical field at 2K.
Explain the working N-P-N transistor. Derive expression for the current and voltage gains.
If E_0 is the peak value of the input voltage V_{in} calculate the output voltage V_{out}.
Distinguish qualitatively between dia-, para-, ferro-, antiferro- and ferrimagnetism. How is the weak and temperature independence paramagnetism of metals explain?
What is the photovoltaic mode of operation for a photo-diode? Describe the construction and working of a silicon solar cell.
Simplify the following logic function and draw the corresponding logic diagram:- Y = (A+B).(A + C).(B+C)
Four silicon diodes are connected as shown in Fig. 1. A sinusoidal voltage of amplitude 2\text{ V} is applied in the input. What is the waveshape of the output and its amplitude? If the amplitude of the input voltage is reduced to 1\text{ V}, what will be the waveshape of the output and its amplitude ? Threshold voltage of each diode is 0.6\text{ V}.
Simplify the following logic function and draw the corresponding logic gates: Y = A.B + B.\overline{C} + \overline{A}.B + \overline{A}.C + \overline{B}.\overline{C} + \overline{A}.\overline{B}.\overline{C} + A.B.C
Draw the circuit of an emitter-follower and find its voltage gain.
Explain the basic distinction between a perfect conductor and a superconductor.
Assuming that for a paramagnetic material, the magnetic susceptibility is inversely proportional to temperature in Kelvin, obtain Curie-Weiss law for the paramagnetic phase of a ferro-magnetic material.
Define ex-OR. Give its truth table and draw the possible logic blocks.
Derive the expression for the frequency spectrum of a carrier wave of frequency f_c which is amplitude modulated by a frequency f_m. A certain transmitted radiates 9\text{ kW} of power when the carrier wave is unmodulated and 10.12\text{ kW} power when the carrier wave is sinusoidally modulated. Calculate the modulation index.
A Si BJT is connected as shown Fig . Show that it is in active region and works as an amplifier Calculate its mid frequency gain, given that BJT has h_{ie} = 1\text{ k}\Omega, h_{oe} = h_{re} = 0, I_{co} = 20\text{ nA}.
Draw the block diagram of a superhetro dyne radio receiver and explain the function of local oscillator.
How does build in potential appear across a p-n junction? Explain under what biasing conditions drift and diffusion currents, respectively, dominate.
Establish the two Barkhausen conditions for sustained sinusoidal oscillations. Sketch the circuit of Wien's bridge oscillator and explain its working.
Draw a circuit using AND, OR and NOT gate to realize the following truth table: \begin{array}{|c|c|c|c|} \hline \multicolumn{3}{|c|}{\text{INPUTS}} & \text{OUTPUT} \\ \hline A & B & C & Y \\ \hline 0 & 0 & 0 & 0 \\ 0 & 0 & 1 & 1 \\ 0 & 1 & 0 & 1 \\ 1 & 0 & 0 & 1 \\ 0 & 1 & 1 & 0 \\ 1 & 0 & 1 & 0 \\ 1 & 1 & 0 & 0 \\ 1 & 1 & 1 & 1 \\ \hline \end{array}