Kurukshetra University 2007 B.Tech Electronics and Communications Engineering Semiconductor Devices and Circuits (SDC) - Question Paper

Semiconductor Devices and Circuits
Paper—ECE-201E
Time: 3 Hours
Maximum Marks: 100

Note :- Attempt any 5 ques.. All ques. carry equal marks.

1.(a) What is regulated power supply ? Draw its block diagram and provide function of every block. [10]

(b) What is meant by TUF of a rectifier ? Derive its value for half wave and bridge rectifier. [10]

2.(a) Show that the maximum d.c. output power in a half wave circuit occurs when the load resistance equals the diode resistance RF [10]

(b) (i) For what voltage will the reverse in a p-n junction Ge diode reach 90% of its saturation value at room temperature ? [3]

(ii) What is the ratio of the current for a forward bias of 0 05 V to the current for the identical magnitude of reverse bias. [3]

(iii) If the reverse saturation current is 10 micro A, compute the forward currents for voltages of 0.1, 0.2 and 0.3 V respectively. [4]

3. (a) Sketch 2 RC-coupled CE transistor stages. Show the low freq. model for 1 stage. What is the expression for fL ? [10]


(b) provided :
IE = 2.5 mA,
hfe = 140,
hoe = 20 micro S (micro mho) and
hob= 0 five micro S
Determine:

—the common emitter hybrid equivalent ckt— the common base Re model. [10]

4.(a) Draw fixed bias ckt. discuss why the circuit is unsatisfactory if the transistor is changed by a different of the identical kind. [5]

(b) In a certain transistor 99 6% of the carriers injected into the base cross the collector base junction. If the leakage current is five micro A and the collector current is 20 mA. compute at alpha d.c. and the emitter current. [10]

(c) What is sensistor ? discuss how it can be employed in a transistor ckt. to compensate the variation of operating point with temperature. [5]

5.(a) What do you mean by voltage amplifier and current amplifier ? provide their equivalent ckt. [5]

(b) Classify amplifiers based on Sting point selection. Compare different configurations in terms of efficiency and distortion. [10]

(c) For a class B amplifier providing 20 V peak signal to a 16 ohm load (speaker) and a power supply of Vcc = 30 V. Determine the input power, output power and ckt. efficiency. [5]

6.(a) Draw the ckt. diagram of a crystal oscillator and discuss its operation in detail. [10]

(b) explain the advantages add limitations of a resonant ckt. sinusodial oscillator. [10]

7.(a) discuss 2 biasing circuit for JFET. discuss under what circumstances every of these are used. [10]

(b) describe transconductance, drain resistance and amplification factor of a FET and derive the relation ranging from them. [10]

8.(a) Distinguish ranging from depletion and enhancement MOSFET. [10]

(b) (i) A JFET has a drain current of six mA if

IDSS = 12 mA and
Vp = - four V obtain VGS. [5]

(ii) Por an n-channel FET

IDSS = 5.8 mA,
Vp = three V and
VGS = -2 V
obtain ID, gm, gmo [5]

Earning:   Approval pending.