Ql. In a long semiconductor bar (EG 2 conduction band electrons come in from the left in the positive x-direction with a kinetic energy of 3 eV. They move from location A to B to C to D. Between A and the electric field is zero; between locations B and there is a linearly varying voltage increase of 4 between C and the field is again zero. Assuming no scattering, sketch a simplified band diagram describing the motions of these electrons. Assuming that these electrons can be described as plane waves, with a free-electron mass, write down the wave function of the electrons at location D. Leave your result in terms of an arbitrary normalization constant. Assume the mass of free electron to be 9·11 X 10^-31 kg.
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Calculate the Fermi energy EFo at 0ºK for copper and estimate the average speed of the conduction electrons in Cu. The density of Cu is 8·96 gm/cm^3 and .atomic weight is 63·5.· Given Avogadro's number is
6 X 10^23.


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In the common source amplifier shown, evaluate voltage gain Av given


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Define lumen and candela. The wavelength of visible light ranges from violet at approximately 380 nm to red at 720 nm. Obt.aìn the bandwidth available of visible light.

Implement the following expression using NAND gates only
Y

Q2.
For the MOSFET characteristic shown in the figure, calculate


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What is compensated doping
An n-type semiconductor containing 10^16 phosphorus (donor) atoms/cm3 has been doped with 10^17.boron (acceptor) atoms/cm^3. Calculate the electron and hole concentrations in the semiconductor.


Define Fan-in and Fan-out with an example. Draw the circuit diagram of an NMOS circuit to realize f ac.

Q3.
Consider the ac equivalent circuit of a MOSFET Colpitts
oscillator.

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Derive the expression for oscillation frequency. Also find the condition on the gain to initiate the oscillations spontaneously.




As per the Barkhausen criterion, the positive feedback exists over a particular · frequency range arid 'the resulting feedback signal reinforces the error signal. Explain the phenomenon which limits the amplitude of the oscillations under steady state.

A typical 1 MHz quartz crystal has the following properties:
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The two frequencies are called series and parallel resonant
frequencies. In the equivalent circuit, Co is parallel with LCR.

What are C and L in the equivalent circuit of the crystal

What is the quality factor Q of the crystal


What is a multiplexer Write the symbol and truth table of a 4-to-l multiplexer. Implement the same using logic gates.


Q4.(a)
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If 1/t is defined as the mean probability per unit time that an electron is scattered, show that the mean time between collisions is


The transistor circuit shown has ß 100, VBE(active) 0·7 V. Find the operating point and the mode of operation when S1, S2 are closed and S1, S2 ere open.

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Find the diode current in the circuit shown below when the diode has cut in voltage,


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Q5. Find the Thevenin resistance for the circuit shown below by zeroing the sources. Then, find the short-circuit current and the Thevenin equivalent circuit.

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A voltmeter and an ammeter are to be used to determine the power dissipated in a resistor. Both the instruments are guaranteed to be accurate within at full-scale deflection. If the voltmeter reads 80 V on its 150 V range and the ammeter reads 70 mA on its 100 mA range, determine the limiting error for the power calculation.


The following measurements pertain to a two-port circuit operating in the sinusoidal steady state. With port 2 open, a voltage equal to 150 cos 4000t V is applied to port l. The current into port 1 is 25 cos (4000t 45º) and the port 2 voltage is 100 cos (4000t V. With port 2 short-circuited, a voltage equal to 30 cos 4000t ·v is applied to port l. The current into port 1 is 1·5 cos (4000t 30º) and the current into port 2 is 0·25 cos (4000t 150º) A. Find the parameters that can describe the sinusoidal steady-state behaviour of the circuit.

For the circuit shown in -the figure, find the branch currents I1, I2 and I3 using Mesh analysis.

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Briefly discuss only the basic principles of a Thermistor and Thermocouple.

Explain why a semiconductor has a negative resistance coefficient.

Q6.
Use source transformations to aid in solving for the currents i1 and i2 shown in the circuit below.

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Find the phasor voltage and the phasor current through each element in the circuit shown in the figure.

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Find the equivalent resistance and capacitance that causes a Wien bridge to null with the following component values:

R1 3·1kn, R3 25 kn, R4 100 kn
C1 5·2 µF and f 2·5 kHz



The voltage source Vg drives the circuit shown in the figure. The response signal is the voltage across the capacitor, Vo. Calculate the numerical expression for the transfer function.

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Write down the incidence matrix and cut-set matrices for the network shown below.

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Q7. A certain 5-hp three-phase induction motor operates from a 440-V-rms (line-to-line)·three-phase source and draws a line current of 6·8A rms at a power factor of 78 percent lagging under rated full load conditions. The
full load speed is 1150. rpm. Under no-load ·conditions, the· speed is 1195 rpm, and the line current is 1·2 A rms at a power factor of 30 percent lagging. Find the power loss and efficiency with full load, the input power with no load, and the speed regulation.


Explain the operation of a Voltage-to-Frequency Converter. Give the primary advantages and limitations of voltage-to-frequency converters.

The relationship between the input voltage V¡ and the output frequency f for the VCO is given as V¡= f/50.
If 530 pulses are passed by the AND gate during 0·1 sec gating pulse, what is the amplitude of V¡?



For the circuit shown in the figure below, let 15 V.


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Compute V1 and V2 in the circuit shown below.

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Q8.
Two coils are wound on a toroidal core as illustrated in the figure below. The reluctance of the core is 10^7(ampere-turns)/wb Determine the self-inductances and mutual inductance of the coils. Assume that the flux is confined to the core so that all of the flux links both the coils.
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Consider the source, transformer and load shown in the figure below. Determine the rms values of the currents and voltages, with the switch open and with the switch closed.


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Describe sampling oscilloscope and storage oscilloscope in brief.

If, in the figure given below, the distance Y1 is 1·8 cm and Y2 is 2·3 cm, what is the phase angle using the X-Y mode of oscilloscope

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For the S-domain circuit shown in the figure, find the transfer function V0/V¡, the impulse response, the response when and (iv)the response when 8 cos 2t V.


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