ELECTRONIC DEVICES & CIRCUITS (EDC)

ELECTRONIC DEVICE & CIRCUIT
(EDC)
B.Tech EXAMINATION
SEM III, 2012-13
UTTARAKHAND TECHNICAL UNIVERSITY(UTU)

Time: 3 hours

Total marks: 100

Section A

Attempt any four of the following:

1.    Why space charge region is called as depletion region? Which types of carriers are present in the space charge region?

2.    Discuss the working of Schottky diode and hot carrier diode in brief.

3.    A diode is biased at a current of 1 mA.
(a) Determine the current change if V_D changes by 1 mV.
(b) Determine the voltage change if I_D changes by 10%.

4.    Give the Barkhausen condition required in order for sinusoidal oscillator to be sustained.

5.    Derive an expression for the voltage gain of a CE transistor amplifier in terms of h-parameters.

6.    What is the advantage of using quaternary alloy in fabricating LEDs?

Section B

Attempt any two of the following

1.    In an experiment it is desired to obtain equal electron and hole drift currents. How should the carriers densities be chosen? Assume μ_n/μ_p = 1350/480.

2.    For the circuit shown in fig.1, assume β = h_FE =100.Find if the transistor is working in cut-off, saturation or active region.

Fig.1

3.    Determine the voltage gain of the stage shown in fig.2

Fig.2

Section C

Attempt any two of the following:

1.    Of the available common-source, common gate and source follower topology, which one provides a moderate source voltage gain, a high input impedance, and a moderate output impedance? Explain how source degeneration raises the output impedance of CS stage considerably?

2.    Derive the frequency equation of RC phase shift oscillator and how its differ from weinbridge oscillator.

3.    How bootstrapping is achieve and how the stability is achieved with this?

 Section D

Attempt any two parts of the following:

1.   Which are the key parameters that enhance the performance of HBTs? Explain how the magnitude of f₁and f_max varies between HBT and BJT structures.

2.  Explain the function of DC amplifier and transformed coupled amplifier and differentiate them.

3.  Derive the expression of time constant of Bistable multivibrator and discuss monostable multivibrator.

Section E

Attempt any two parts of the following:

1.    What is the relation between the transfer gain with feedback A₁ and that would feedback A? Define the negative feedback. List the five characteristics of an amplifier which are modified by negative feedback.

2.   Explain the working of MESFET. Determine the expression for the voltage at the edge of the depletion region, V(h), in a MESFET device

3.  Consider the circuit shown in Fig.3

     where I_s = 6 x10^-16 A, β = 100, and V_A =∞. Calculate the operating point of Q₁.

Fig.3

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