Biju Patnaik University of Technology 2008-2nd Sem B.Tech (B Tech) , basic electronics . - Question Paper

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(a)    Define mobility and conductivity of an intrinsic semiconductor.

(b)    A diode has a reverse saturation current of 5 M at 25 C fora reverse voltage of 20 V. Calculate the reverse resistance,

fc)	An ideal P*N junction diode acts like a	(0	Convert 25.62510 to its binary equivalent.
	bistable switch Justify.	(j)	What is lime base ? Define deflection
(<J)	Deline ac load lino and dc load line of a npn transistor connected m CE conftgu-		sensitivity of an oscilloscope.
	ratfon. 2.	(a)	Write the analytical equation for the
(e)	How emrtter bypass capacitor in a CE amplifier prevents signal degeneration ?		current which describes both the forward and reverse characteristics of a diode. A
(0	Sketch the JFET drain characteristic with ; VGS = 0. Show the ohmic and pinch-off regions. IVL		silicon diode has a forward voltage drop of 1.2 V for a forward dc current of 100 mA. ft has a reverse current of 1 HA for a
(g)	Derive an expression for the frequency of oscillation of a three stage RC oscillator when the three R and C components are equal.		reverse voltage of 10 V. Calculate the bulk and reverse resistance of the diode. Find the ac resistance at forward dc
(h)	An audio signal given by 15 sin 2* (2000 t)		current of 25 mA. 5
	amplitude modulates a sinusoidal carrier	(b)	Explain how diodes are useful for clamp
	wave 60 sin 2 m(100,0001), Find the modulation index and percent modulation.		ing operation. Draw a negative clamping
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circuit. Find the relation between the time constant of the circuit and the time period of the input signal. What should be the full discharge time, in terms of the time constant of the circuit, for the:,capaciior you have used.    5

3. (a) The following measurements were made in a transistor connected in a circuit.

I_c-10.525 mA ; l_B=100 \xA and i_CBO =

5 HA.

Find the values for a|3_dc and i_E, 5

(b) Draw the circuit of an emitter follower, Derive an expression; far its output impedance. List two applications of an emitter follower.    5

4.    (a) The data sheet for a JFET EndicaTes that

l_03s=16 mA and V_GSfcfr) = - 5V, Find The drain current |_D for V_GS= 0 V, -1 V and -4 V.    4

(b)    What is enhancement mode of n-channel MOSFET ?    2

(c)    Draw the circuit lor CMOS logic inverter, Explain the flow of current and power.

4

5.    (a) An RC coupled amplifier has a midband

frequency gain, of 400 and tower and upper 3 dB frequencies of 100 Hz and 10 kHz. A negative feedback with [1=0.01 is incorporated in the amplifier circuit. Find the gain with feedback and new ba n dwi d lh w i th fe edback.    5

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(&) Wtrft are crystal escalators ? Wfite !he<r charact&nfttic features L*st two applications    5

6 {a) What¹ ii frequency sUiOiirty of an osotlator⁷ Draw the circuit 1or a RC phase shift oscillator. What aroi the advantages ar*d disadvantages of Uits oscillator*> 5

0) Draw a differential ampMer ctrcurt Derrve an expression for rts CMRR, What is the role of emitter resistor ? List two appitca* tions of differential ampler.    5

7, (a) Draw' a differentiator circutt using an OPAMP and derive an expression for its output voltage v₀ in terms oi input vollage v.-    5

(b) Prove the Boolean identity

(A + B)(A + C)= A + BC.    2

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(c) Simplify the Boolean expression. 3 I A * Bjf A + B)f A + C)

8. (a:) ftsaiss AD and OA conversion techniques used tn digital communication.    5

(b) Draw a simplified fibre opto communication system. Explain the principle of operation.    5

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