Download AKTU B-Tech 4th Sem 2015-16 NEC 402 Electronic Circuits Question Paper

Printed Pages: 4 NEC-402

(Following Paper ID and Roll No. to be filled in your Answer Books)

Paper ID: 131406 Roll No.

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B.TECH.

Theory Examination (Semester-IV) 2015-16

ELECTRONIC CIRCUITS

Time : 3 Hours Max. Marks : 100

Section-A

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Q1. Attempt all parts. All parts carry equal marks. (10×2=20)

1. (a) What do you mean by voltage follower circuit ? explain in brief.
2. (b) Why Op Amp is rarely used in open loop configuration?
3. (c) What is Barkhausen criteria for sinusoidal oscillations
4. (d) Draw the current mirror circuit and write its output current equation.

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5. (e) State the properties of negative feedback.
6. (f) What are the advantages of using an active load in diffential amplifier circuit?
7. (g) What are the types of feedback?
8. (h) Draw the Small signal p Model of BJT.
9. (i) How does the slew rate effects Finite or Full power Band Width of Op Amp ?

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10. (j) An enhancement type NMOS transistor with V_t = 0.7V has its source terminal grounded and a 1.5V dc applied to the gate. In what region does the device operate for V_D = 0.9V.

Section-B

Q2. Attempt any five questions from this section. (10×5=50)

1. (a) Discuss the effect of finite loop gain on the performance of non-inverting OP-AMP.
2. (b) A MOSFET is to operate at I_D=.1mA and is to have g_m=1 mA/V. If K_n=50µA/V². Find the required W/L ratio and the overdrive voltage.

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3. (c) Draw the high frequency model of MOSFET and drive an expression of f_H.
4. (d) BJT transistor amplifier stage has R_E=R_C=1.5kO, R_s =600O, R_L =2kO and transistor parameter as ß=100 and r=1kO. Determine the value of C_C1, C_C2 and C_E needed to obtain f_L=50Hz and also draw the circuit.
5. (e) Explain the operation of BJT as a switch and as an amplifier.
6. (f) Explain the Nonideal characteristics of MOS differential pair.
7. (g) Draw a circuit diagram of Wein bridge oscillator and drive an expression of frequency of oscillation. Calculate the frequency of oscillation for given values of R₁=R₂=200KO, C₁=C₂=200pF.

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8. (h) Design the circuit shown in fig.1 so that transistor operates at I_D = 0.4mA and V_t = +0.5V. The NMOS transistor has V_t-0.7V. Cox = 100µA/V², L = 1µm and W = 32µm. Neglect the channel length modulation.
   V_DD =+2.5V
   
   V_SS = -2.5V
   Fig. 1

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Section-C

Note: Attempt any two questions from this section. (15×2=30)

1. Q3. (a) Draw Instrumentation Amplifier. How does it improve the performance parameters of an Op Amp?

Define slew rate and show how it is related to full power bandwidth. An op-amp has a rated output voltage ± 10V and slew of rate of 1V/uS. What is its full power band width.

4. Q4. (a) Consider the common emitter circuit using a BJT having I_S±10^-15A. A collector resistance Rc=6.8 kO and power supply Vcc-10V.
   1. (i) Determine the value of bias voltage V_BE required to operate the transistor at V_CE=3.2V.what is the corresponding value of I_C.

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   2. (ii) Find the voltage gain A_v at this bias point.
   3. (iii) If the input sine wave of 5mA peak amplitude is superimposed one V_BE. Find the amplitude of output sine wave signal.

(b) Draw the circuit for CB amplifier and find expression for short circuit gain.

5. Q5. (a) Draw the T equivalent circuits of common source amplifier with a source amplifier with a source resistance and obtain the expressions for R_in, R_out, and G_v.

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(b) An inverting amplifier has feedback resistor R₂=500KO and R₁=5KO. Find the amplifier circuit voltage gain, input resistance and output resistance. Also find the output voltage and input current if the input voltage is given as .1 volts. Assume the OP-AMP to be an ideal one.

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