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I B.Tech Semester Regular Examinations, June 2009 ELECTRONIC DEVICES AND CIRCUITS (Common to ECE, CSE, EIE, BME, IT, E.CON.E, CSS, ETM, ECC and ICE) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks โ โ โ โ โ
- Analyse the two dimensional motion of an electron in electric field. [16]
- (a) Explain about semiconductor, Insulator & Conductor with neat sketch. (b) State the Einstein relationship for semiconductor. (c) State paulis exclusion principle. [6+5+5]
- Draw the circuit diagram of a FWR:
(a) With centre tap connection and (b) Bridge connection and explain its operation. [16]
- With necessary diagram explain the input & output characteristics of common emitter configuration. [16]
- (a) What is the importance of dc load line? (b) The figure 5b shows that D.C bias circuit of a common Emitter transistor amplifier. Find the percentage changer in collector current, if the transistor with HF E = 50 is replaced by another transistor with HF E = 150. It is given that the base emitter drop VBE = 0.6V. [8+8]
Figure 5b
- (a) Draw the low frequency hybrid equivalent. Circuit for CE & CB amplifier.
(b) Give the approximate h-parameter conversion formulae for CB and CC con- figuration in terms of CE. (c) Give the advantages of h-parameter analysis. (d) Give the procedure to form the approximate h - model from exact h - model of amplifier. [4+6+3+3]
- (a) How the distortion is decreased in negative feedback?
(b) An amplifier has an open loop gain of 1000 and a feedback ration of 0.04. if the open loop gain changes by 10% due to temperature, find the percentage change in gain of he amplifier with feed back. [10+6]
- Draw a neat circuit diagram of RC phase shift oscillator using BJT and explain its working principle. [16]
- (a) Find the values of hfb and hfc, if the value of hfe of a transistor is 50.
(b) A transistor is connected in CC configuration and its h-parameters are hie = 1100 ฮฉ, hre = 2.5 ร 10 โ^4 , hf e = 50, hoe = 24mA/V, the circuits uses RL = 10 K ฮฉ, and Rs = 1 K ฮฉ, calculate gain Ai, input resistance Ri and voltage gain Av of this amplifier. [4+12]
- Draw the practical circuit for Current shunt feedback and find the voltage gain, input impedance & output impedance. [16]
- Prove that the feedback โฮฒโ of the phase shift network is given by
- ฮฒ = (^1) โ 5 ฮฑ (^2) โ^1 j(6ฮฑโฮฑ (^3) ) Where ฮฑ = (^) W CR^1
Assume that the network does not load the amplifier. [16]
I B.Tech Semester Regular Examinations, June 2009 ELECTRONIC DEVICES AND CIRCUITS (Common to ECE, CSE, EIE, BME, IT, E.CON.E, CSS, ETM, ECC and ICE) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks โ โ โ โ โ
- (a) What is deflection Defocusing? Give the reasons of defocusing. (b) Compare: Electrostatic deflection and magnetic deflection (c) An electron beam is deflected of 10^0 degrees when it traverses in uniform magnetic field, 3 cm wide, having a density of 0.6 mT. Calculate: i. The speed of the electrons and ii. The force on each electron. The direction of the beam is normal to that of the flux. [4+6+6]
- (a) Explain about diffusion capacitance in detail. (b) Derive an expression for diffusion capacitance. [5+11]
- Derive all the necessary parameters of HWR. [16]
- (a) Define a Transistor. (b) What are the differences between Bipolar Junction transistor & Field effect Transistor? (c) Write any two applications of transistor. [5+7+4]
- (a) Explain the simpler way of drawing dc load line. (b) Calculate the de bias voltage and currents in the circuit shown in figure 5b (Neglect VBE Of Transistor). [8+8]
I B.Tech Semester Regular Examinations, June 2009 ELECTRONIC DEVICES AND CIRCUITS (Common to ECE, CSE, EIE, BME, IT, E.CON.E, CSS, ETM, ECC and ICE) Time: 3 hours Max Marks: 80 Answer any FIVE Questions All Questions carry equal marks โ โ โ โ โ
- Derive the expression for the deflection in an electrostatic deflection system. Hence obtain the expression for electro static deflection sensitivity. [16]
- (a) Define Mass Action Law. (b) Explain N type & P type Semiconductors. [4+12]
- (a) Write a short notes on multiple L- Section and multiple ฮ - Section Filter. (b) Compare all the filter circuits from the point of view of ripple factor. [10+6]
- (a) Define DC drain resistance. (b) Define AC drain resistance. (c) Define trans conductance. (d) Define amplification factor. [4+4+4+4]
- (a) Find the collector current and collector to emitter voltage for the given circuit as shown in figuer 5a.
Figure 5a (b) Can the value of stability factor be less than unity? Explain briefly. [10+6]
- (a) Write a short notes on millers theorem.
(b) Analyse a single stage transistor amplifier using h - parameters. [8+8]
- An amplifier has a gain of 300. when a negative feedback is applied the gain is reduced to 240. Find the feedback ratio. [16]
- Explain briefly about frequency and amplitude stability of oscillators. [16]
