Paper 8

Core VIII: Analog Systems

Old CBCS Core VII: Analog Systems and Applications

(Semiconductor diodes, devices and their applications, transistors and amplifiers, coupled amplifier and its application in feedback circuit, operational amplifier and its application.)

Syllabus

Unit 1
  • Semiconductor Diodes: P and N type semiconductors, energy level diagram, conductivity and Mobility, Concept of Drift velocity, PN junction fabrication (simple idea), Barrier formation in PN Junction Diode, Static and Dynamic Resistance, Current flow mechanism in Forward and Reverse Biased Diode, Drift velocity, derivation for Barrier Potential, Barrier Width and current Step Junction.
  • Two terminal device and their applications: (1) Rectifier Diode: Half-wave Rectifiers. center- tapped and bridge type Full-wave Rectifiers, Calculation of Ripple Factor and Rectification Efficiency, L and C Filters (2) Zener Diode and Voltage Regulation, Principle and structure of LEDS, (2) Photo diode (3) Solar Cell.
Unit II
  • Bipolar Junction Transistors: n-p-n and p-n-p transistors, Characteristics of CB, CE and CC Configurations, Current gains a and b, Relation between a and b, Load line analysis of Transistors, DC Load line and Q-point, Physical mechanism of current flow, Active, Cut-off and Saturation Regions.
  • Transistors Biasing: Transistor Biasing and Stabilization circuits, Fixed Bias and Voltage Divider Bias.
  • Amplifiers: Transistors as 2-port network h-parameter Equivalent Circuit, Analysis of a single stage CE amplifier using Hybrid Model, Input and Output impedance, Current, Voltage and Power Gains.
Unit III
  • Classification of class A, B and C amplifiers, Push-pull amplifier (class B).
  • Coupled Amplifier: RC-coupled amplifier and its frequency response.
  • Feedback in Amplifiers: Effect of Positive and Negative Feedback on Input Impedance, Output Impedance, Gain Stability, Distortion and Noise. Sinusoidal Oscillations: Barkhausens criterian for self-sustained oscillations. RC Phase shift oscillator, determination of Frequency, Hartley and Colpitts oscillators.
Unit IV
  • Operational Amplifiers (Black Box approach): Characterist ics of an Ideal and Practical OP-AMP (IC741). Open-loop and Closed loop Gain. Frequency Response. CMRR, Slew Rate and concept of virtual ground.
  • Applications of Op-Amps: (1) Inverting and non-inverting amplifiers (2) Adder (3) Subtractor (4) Differentiator, (5) Integrator (6) Log amplifier, (7) Zero crossing detector (8) Wein bridge oscillator.
Text Books
  • Foundations of Electronics - Raskhit and Chattopadhyay (New age International Publication)
  • Concept of Electronics - D. C. Tayal (Himalay Publication)
Reference Books:
  • Electronic devices and circuits R. L. Boylstad (PearsonIndia)
  • Electronic Principles - A.P. Malvino (Tata McGrawHill)
  • Principles of Electronics - V. K. Mehta and Rohit Mehta (S. Chand Pub- lication)
  • OP-Amps and Linear Integrated Circuit - R. A. Gayakwad (PrenticeHall)
  • Physics of Semiconductor devices - Donald A. Neamen (PrenticeHall)
  • Analog System and Application- Gupta Kumar, Pragati Prakashan

Questions

2024 | +3-III-S-CBCS(MS)-Sc(H)-Core-VII-Phy | FM 60

Part-I | Answer allthequestions | 1x8
  • The inductor opposes alternating current to pass through it. (True/False)
  • Maximum efficiency of half-wave rectifier is ______.
  • The intersection point of DC load line with output characteristic is called __.
  • Cut-off point is the intersection of $I_B =0$ curve with ______.
  • Barkhausen's criterion for self-sustained osciliation is given by __.
  • The positive feedback causes system stability. (True/ False)
  • Which acts as feedback network for Wein bridge oscillator ?
  • The voltage gain of an OP-AMP without feedback is called ______ voltage gain.
Part-II | within two to three sentences | 1.5x8
  • What is step junction ?
  • Define mobility.
  • Draw DC load line for a common emitter NPN trnasistor.
  • Draw symbol of PNP and NPN transistor.
  • Find $\alpha$, if $\beta = 50$.
  • Define bandwidth of RC-coupled amplifier.
  • Show that positive feedback increases output noise in amplifier.
  • Define slew rate.
  • What is zero crossing detector?
  • Write two applications of integrator.
Part-III | in maximum 75 words | 2x8
  • Discuss about capacitor filter.
  • Discuss construction of N-type semiconductor.
  • Explain briefly working of a photodiode.
  • Draw input and output characteristics of a transistor in common base mode.
  • Discuss classification of amplifiers based on mode of operation.
  • The voltage gain of an amplifier is 4000. Find the voltage gain of the amplifier when negative feedback is applied in the circuit. Given $\beta = 0.04$.
  • Discuss operation of tank circuit with circuit diagram.
  • Calculate frequency of oscillations and feedback fraction for Hartley oscillator if in its tank circuit C=20 pF, L1= 100 mH, L2 = 1000 mH and M= 20 mH.
  • Discuss OP-AMP as differentiator.
  • Determine the voltage gain for the common mode input signal of an OP -AMP if V1=4mV, V2=6mV and V0 = 15 mV.
PART-IV | Answer within 500 words each | 6x4

4) With neat diagram explain the I-V characteristic of PN diode in forward and reverse biased conditions.
OR
With neat circuit diagram explain the principle and working of center-taped full wave rectifier.

5) Describe voltage divider method of transistor biasing and find the expression for stability factor.
OR
With neat circuit diagram explain the principle and working of push-pull amplifier (class B).

6) With neat circuit diagram discuss working of RC-coupled amplifier. Also derive expression for high frequency voltage gain and upper cut-off frequency.
OR
With neat circuit diagram explain the principle and working of Colpitts oscillator.

7) Find the expression for common mode rejection ratio (CMRR) of OP-AMP. Also discuss characteristics of OP-AMP IC-741 and draw its block diagram.
OR
Discuss about Wein-bridge oscillator. Find the expression for frequency of oscillation and condition for sustained oscillation.

Working of RC-coupled amplifier. Also derive expression for high frequency voltage gain and upper cut-off frequency.
OR
With neat circuit diagram explain the principle and working of Colpitts oscillator.

  1. Find the expression for common mode rejection ratio (CMRR) of OP-AMP. Also discuss characteristics of OP-AMP IC-741 and draw its block diagram.
    OR
    Discuss about Wein-bridge oscillator. Find the expression for frequency of oscillation and condition for sustained oscillation.on for frequency of oscillation and condition for sustained oscillation.

2023 | +3-III-S-CBCS(MS)-Sc(H)-Core-VII-Phy-R&B | Full Marks: 60

PART-I | Answer the following questions. | 1×8
  1. The leakage current across a PN-junction is due to _____ carriers.
  2. Drift velocity per unit electric field is known as ______ .
  3. There are _____ h parameters of a transistor.
  4. Class B power amplifier is for _____ cycle of input signal.
  5. The value of negative feedback fraction is always less than ______.
  6. The other name of oscillatory circuit is ______ circuit.
  7. The input stage of an OP-AMP is usually a ______ amplifier.
  8. What is the frequency range of IC-741 OP-AMP?
PART-II | Answer any eight within two to three sentences. | 1.5x8
  1. Draw the block diagram of OP-AMP.
  2. Explain importance of CMRR.
  3. Explain gain stability.
  4. A crystal has a thickness of 't' mm. If the thickness is reduced to 1%, what happens to frequency of oscillations.
  5. State Barkhausen criterion.
  6. Define current amplification factor.
  7. Calculate $I_{E}$ in a transistor for which $\beta = 50$ and $I_{B} = 20 \mu A$.
  8. Explain stability factor.
  9. A half wave rectifier supplies power to 1k$\Omega$. The output supply voltage is 220 $V_{rms}$ Calculate $E_{dc}$ neglecting forward resistance of the diode.
  10. Explain Dynamic resistance of PN-junction.
PART-III | Answer any eight of the following (in maximum 75 words.) | 2 × 8
  1. Explain Rectification efficiency.
  2. Explain PN - junction diode is a one way device.
  3. Derive an expression for R.M.S. current of full wave rectifier.
  4. Write gain and Transistor configuration.
  5. For a certain transistor, $I_{B} = 20 \mu A$, Ic = 2mA and $\beta = 80$ , find $I_{CBO}$ .
  6. Explain the function of coupling capacitors.
  7. Determine the frequency of oscillations of RC-phase shift Oscillator if each RC section has R = 2m$\Omega$ and C = 40nF.
  8. For an OP-AMP, Ad = 2000 and $A_{cm} =40$ Find the value of CMRR.
  9. Write advantages of non-inverting amplifier with finite-loop gain.
  10. Write different characteristes of an ideal OP-AMP.
PART-IV | Answer within 500 words each. | 6x4

  1. Explain the fabrication of PN-junction. Then discuss about the current flow mechanism in forward and reverse biased diode.
    OR
    With neat circuit diagram describe the construction and working of bridge type full wave Rectifier.

  2. With neat circuit diagram describe the construction, working and characteristics of N-P-N transistor in CE mode.
    OR
    With neat circuit diagram describe the equivalent circuit of a CE amplifier using hybrid model.

  3. Explain principles of negative voltage feedback in amplifiers and gain of negative voltage feedback amplifier.
    OR
    With neat circuit diagram describe the working, advantages and disadvantages of RC phase shift oscillator.

  4. What do you mean by operational amplifier. Explain it with block diagram and circuit symbol.
    OR
    With neat circuit diagram describe OP-AMP as substractor and Integrator.

2022 | +3-III-S-CBCS(MS)-Sc(H)-Core-VII-Phy-R&B | Full Marks : 60

PART-I | Answer all questions | 1x8
  1. Maximum efficiency of full wave rectifier is _____.
  2. Zener diode is used as voltage regulator in _____ biased mode.
  3. For faithful amplification the collector-emitter should be above ______ voltage.
  4. The intersection point of DC load line with the output characteristics is called ______.
  5. Hartley oscillator generates waveforms in ______ frequency range.
  6. In which frequency range voltage gain of RC-coupled oscillator is independent of frequency.
  7. The circuit in which the output changes when input voltage crosses 0 V, is called ______.
  8. OP-AMP is operated with _____ feedback.
PART-II | Answer any eight within two to three sentences | 1.5x8
  1. Find conductivity n-type germanium having donor density, $n_d =10^{20}\, atoms/m^3$ and mobility, $\mu=0.38$.
  2. Define dark current of photodiode.
  3. Discuss advantages of light emitting diode (LED) over incandescent lamp.
  4. Find value of $\alpha$, if $\gamma= 20$.
  5. Distinguish class-A, class-B and class-C amplifiers.
  6. Define bandwidth of RC-coupled amplifiers.
  7. Why positive feedback is not used in amplifier ?
  8. Define slew rate.
  9. Write the characteristics of ideal OP-AMP.
  10. In an inverting OP-AMP. $R_i =3K\Omega$ and $R_f = 600\Omega$. Find the closed loop voltage gain.
PART-III | Answer any eight of the following (in maximum 75 words.) | 2x8
  1. Discuss briefly working principle of solar cell.
  2. Discuss barrier formation in PN iunction diode.
  3. Calculate emitter current ($I_E$) in a transistor if $\beta = 60$ and base current $(I_B) = 30 \mu A$.
  4. Draw input and output characteristics of a transistor in common base configuration.
  5. What is faithful amplification ? Write the various conditions for faithful amplification.
  6. Determine the frequencv of oscillation of RC phase shift oscillator if each RC section has R=2 m$\Omega$ and C= nF.
  7. Prove that negative feedback improves the stability of gain of an amplifier.
  8. The voltage gain of an amplifier is 4000. Find the voltage gain of the amplifier when negative feedback is applied in the circuit. Given $\beta = 0.4$.
  9. Give the block diagram and symbol representation of OP- AMP.
  10. Discuss operation of OP-AMP as differentiator.
PART-IV | Answer within 500 words each | 6x4

  1. With circuit diagram describe construction and working of half- wave rectifier and also find its efficiency. Also define ripple factor.
    OR
    Derive expression for barrier potential for a step junction.

  2. Describe voltage divider bias method of transistor biasing and find an expression for stability factor.
    OR
    With circuit diagram, discuss the working of class-B push-pull amplifier. Also find its efficiency.

  3. With circuit diagram, discuss the working of Colpitts oscillator. Find an expression for its frequency of oscillations.
    OR
    Derive expressions for low frequency voltage gain and low cut-off frequency of an RC-coupled amplifier.

  4. What do you mean by common mode rejection ratio (CMRR)? Find an expression for CMRR of an OP-AMP. Also discuss about IC-741.
    OR
    Discuss about Wein-bridge oscillator. Find the expression for frequency of oscillation and condition for sustained oscillation.

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