Electronic Devices - Dec 2012

Electronics Engineering (Semester 3)

TOTAL MARKS: 80
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Assume data if required.
(4) Figures to the right indicate full marks.

Attempt any four from the following

1 (a) sketch the circuit diagram of zener diode voltage regulator. Briefly explain the circuit operation and the effect of load current.(5 marks) 1 (b) Explain the difference between the clipping and the clapping circuit.A positive voltage clamping circuit and a positive shunt clipping circuit each have a ? 12volt square wave input.sketch the output waveform for both the circuit(5 marks) 1 (c) Explain the selection of a Q point for transistor bias circuit and discuss the limitation of output voltage swing (5 marks) 1 (d) Explain the following characteristic listed on the datasheet: V_cbo,V_ceo,V_ebo,V_ce(sat)

(5 marks) 1 (e) Define the forward transfer admittance ,transconductance,output admittance and drain resistance of fet(5 marks) 2 (a) Using transistor BC 147 A,design a single stage CE amplifier with Av?100, V=3 Volts, fl=15Hz, Sico ?10.(15 marks) 2 (b) For an amplifier in (a) calculate Av, Rin,and maxium possible undistorted output voltage(5 marks) 3 (a) Using mid point biasingmethod design single stage CS AMPLIFIER FOR Av=11 and Vo=4.5volts .Use BFW11,Vgsq=0.3volts,Rl=120kohms,Vdd=20volts(12 marks) 3 (b) For above designed circuit with Rs unbypassed determine voltage gain, input impedence,output impedence,and output voltage for input 1vpp(8 marks) 4 (a) A single phase full wave rectifier use semiconductor diode.The transformer voltage is 35 Vrms to center tap.The load consist of 40uf capacitor in parallrl with 250 ohm resistor. Assume the power line freq to be 50 hz .Calculate
1.The dc current Idc
2.Peak to peak amplitude of ripple voltage
3.The rms value of ripple voltage
4.Ripple factor of rectifier filter output
(10 marks) 4 (b) Explain input protection method in MOSFET(10 marks) 5 (a) If the silicon transistor is used in the circuit as the value hfe=B=30Determine
1.1. whether the transistor is in cutoff ,active or saturation for V1=12Volts, V2=-12volts,Vcc=12volts,R1=15k,R2=100k,Rc=2.2k.also find Vo
2. Find mimium value of R1` for which the transistor is in active region.compute Vo for R1=50K
:- IMAGE(10 marks) 5 (b) Explain zero temperature drift in JFET.(10 marks) 6 (a) Explain various method of biasing of Jfet and mosfet(15 marks) 6 (b) Explain the concept of thermal runaway.(5 marks)

Write Short note

7 (a) Power Mosfet,characteristic ,rating and application(5 marks) 7 (b) Schottkey diode characteristic rating and application(5 marks) 7 (c) CLC Filter(5 marks) 7 (d) BJT as a switch(5 marks)