Cochin University of Science and Techology (CUST) 2007 B.Tech Electronics and Communications Engineering BASIC ELECTRONICS - Question Paper
BTS-n- (S)-07 - 068
B. Tech Degree II Semester (Supplementary) Examination,
(New Scheme: 1996 & 1997 Admissions)
Time: 3 Hours Maximum Marks: 100
I. (a) What are active and passive components? Name atleast two in each category. (6)
(b) Explain the colour code of resistors. What do you mean by tolerance in resistors?
Explain important specification of resistors. (8)
(c) What are fixed resistors? Explain any two types of fixed resistors. (6)
OR
U. (a) Explain the construction and characteristics of the following type of capacitors
(i) Mica capacitor (ii) Electrolytic Capacitor (8)
(b) Explain the following
(i) Chokes (ii) AFCs (iii) RFCs (6)
(c) Explain about variable inductors. (6)
HI. (a) When the wavelength of incident radiation on a photo-electric emitter is changed from 6000A to 7,500A , the maximum kinetic energy of emitted electrons reduces by 30%. Determine die work function of the emitter and the maximum kinetic energy in the two cases. (8)
(b) Explain cold-cathode emission. (6)
(c) Explain Thermionic emission and the Schottky effect. (6)
OR
IV. (a) Define deflection sensitivity of a CRT and derive the expression for deflection
sensitivity. (12)
(b) Explain the application of CRO in die
(i) Measurement of phase difference
(ii) Frequency of a voltage signal (8)
V. (a) State Mass-action law. (2)
(b) A specimen of Ge at 300K for which the density of carriers is 2.5 x 1013/cm3
is doped with impurity atom such that, there is one impurity atom for 10 Ge atoms.
All the impurity atoms may be assumed ionized. The resistivity of doped material is
0.039Cicffi. Carrier mobility for Ge at 300K is 3,600 . For the doped material,
find the electron and hole densities, e * 1,602x 10l9C. (10)
(c) With the help of diagrams, explain the Fermi Level in N-typc and P-type semi conductors. (8)
OR
VI. (a) Explain the following in connection with a PN Junction.
(i) Breakdown Voltage (ii) Knee Voltage
(iii) Maximum forward current (iv) PIV
(v) Maximum power rating (5)
(b) Explain Transition capacitance and diffusion capacitance (6)
(d) Define Zener and Avalanche break downs and explain the V-l characteristics of a
Zener diode. (9)
(Turn Over)
2
VII. (a) Explain early effect and Base-width modulation. (4)
(b) Explain the following
(1) DC load line (ii) ac load line
(Hi) Quiescent points (6)
(c) In a transistor circuit load resistance is 5KCl and quiescent current is 1.2MA.
Determine the operating point when die battery voltage VCC * 12V. How will the
Q-point change when die load resistance is changed from 5KQ to 7.5 KCk. (10)
OR
VIII. (a) Explain the voltage divider bias, and derive the required equations. (8) (b) A voltage divider biasing circi'it using PnP Germanium transistor with fi 44 has
Vcc=4.5V,Rc = 1.5k, Re = 2700, = 27*, =2.1K.
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(i) Find the quiescent point
(ii) Find the quiescent point taking into account die base spreading resistance of 690 O. (12)
IX. (a) Explain the working of a full wave rectifiei (centre tapped). Derive the expression for
(i) the dc load voltage Vde
(ii) the dc load current Ide
(iii) RMS values of currents and voltages
(iv) PIV (10) (b) Show that in a half wave rectifier, maximum dc power o/p defined by Pde-Vdelde,
occurs when RL = RF, where RL is the load resistance and RF is the forward resistance of the diode. (10)
OR
X. (a) Design a dc power supply using half-wave rectifier with capacitor filter to give a dco/p
voltage of 15V at 10MA from a 230V, SOHz ac mains. The ripple content must be less than 1%. (15)
(b) What is a bieader resistor? What function can if serve in a power supply? (5)
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| Earning: Approval pending. |
