MODULE IMPORANT for engineering 2 ESC.pptx

EC module 4 Electronics and Communication

1. THE NATIONAL INSTITUTE OF ENGINEERING DEPARTMENT OF ELECTRONICS AND COMMUNICATION ENGINEERING Course: Introduction to Electronics Engineering Course Instructor Mrs.Shruthi K S Assistant Professor Dept. of ECE NIE, Mysuru 10/12/2023 Dept. of ECE, NIE Mysuru 1 Module – 2 Operational amplifiers & Oscillators

2. 10/12/2023 Dept. of ECE, NIE Mysuru 2 Course Structure: Module – 2: Operational amplifiers & Oscillators Operational amplifiers Oscillators Ideal op-amp Introduction to Oscillators Characteristics of ideal and practical op-amp Crystal controlled oscillators Practical op- amp circuits: inverting and non-inverting amplifiers Voltage follower Summer Subtractor Integrator Differentiator

3. 10/12/2023 Dept. of ECE, NIE Mysuru 3 Operational amplifiers Operational amplifiers are analogue integrated circuits designed for linear amplification that offer near-ideal characteristics. Operational Amplifier , also called as an Op-Amp , is an integrated circuit, which can be used to perform various linear, non-linear and mathematical operations . An op-amp is a direct coupled high gain amplifier . The term operational amplifiers was originally used for d.c amplifiers which perform mathematical operations such as : Summation Subtraction Integration and Differentiation in analog computers.

4. 10/12/2023 Dept. of ECE, NIE Mysuru 4 Operational amplifiers These operational amplifiers can also be used for: a.c to d.c conversion A to D and D to A conversion Signal conditioning Instrumentation Active filters design Special system design

5. 10/12/2023 Dept. of ECE, NIE Mysuru 5 Operational amplifiers Ideal op-amp Symbols and connections Fig: Symbol for an operational amplifier

6. 10/12/2023 Dept. of ECE, NIE Mysuru 6 Operational amplifiers Ideal op-amp Symbols and connections Fig: Pinout diagram of LM741 operational amplifier

7. 10/12/2023 Dept. of ECE, NIE Mysuru 7 Operational amplifiers Ideal op-amp Symbols and connections Fig: Supply connections for an operational amplifier

8. 10/12/2023 Dept. of ECE, NIE Mysuru 8 Operational amplifiers Operational amplifier parameters Before we take a look at some of the characteristics of ‘ideal’ and ‘real’ operational amplifiers it is important to define some of the terms and parameters that we apply to these devices. Open-loop voltage gain The open-loop voltage gain of an operational amplifier is defined as the ratio of output voltage to input voltage measured with no feedback applied. In practice, this value is exceptionally high (typically greater than 100,000) but is liable to considerable variation from one device to another. Open-loop voltage gain may thus be thought of as the ‘internal’ voltage gain of the device , thus: A V(OL) = where A V(OL) is the open-loop voltage gain , V OUT and V IN are the output and input voltages , respectively, under open-loop conditions .  

9. 10/12/2023 Dept. of ECE, NIE Mysuru 9 Operational amplifiers Operational amplifier parameters The open-loop voltage gain is often expressed in decibels (dB) rather than as a ratio. A V(OL) = 20 log 10 Most operational amplifiers have open-loop voltage gains of 90 dB or more . Closed-loop voltage gain The closed-loop voltage gain of an operational amplifier is defined as the ratio of output voltage to input voltage measured with a small proportion of the output fed-back to the input (i.e. with feedback applied ). The effect of providing negative feedback is to reduce the loop voltage gain to a value that is both predictable and manageable. A V(CL) = A V(CL) = 20 log 10 The closed-loop voltage gain is normally very much less than the open-loop voltage gain .  

10. 10/12/2023 Dept. of ECE, NIE Mysuru 10 Operational amplifiers Problem 1 An operational amplifier operating with negative feedback produces an output voltage of 2V when supplied with an input of 400μV. Determine the value of closed-loop voltage gain. Solution: A V(CL) = A V(CL) = 20 log 10 A V(CL) = 2 / 400 * 10 ^-6 A V(CL) = 5000 A V(CL) = 20 log 10 (5000) = 74dB  

11. 10/12/2023 Dept. of ECE, NIE Mysuru 11 Operational amplifiers Input resistance The input resistance of an operational amplifier is defined as the ratio of input voltage to input current expressed in ohms R IN = where R IN is the input resistance (in ohms ), V IN is the input voltage (in volts ) and I IN is the input current (in amps ). The input resistance of operational amplifiers is very much dependent on the semiconductor technology employed. In practice, values range from about 2 MΩ for bipolar operational amplifiers to over 10 12 Ω for CMOS devices.  

12. 10/12/2023 Dept. of ECE, NIE Mysuru 12 Operational amplifiers Problem 2 An operational amplifier has an input resistance of 2 MΩ. Determine the input current when an input voltage of 5 mV is present. Solution: R IN = I IN = I IN = = 2.5nA  

13. 10/12/2023 Dept. of ECE, NIE Mysuru 13 Operational amplifiers Output Resistance The output resistance of an operational amplifier is defined as the ratio of open-circuit output voltage to short-circuit output current expressed in ohms . Typical values of output resistance range from less than 10 Ω to around 100 Ω , depending upon the configuration and amount of feedback employed. R OUT = where R OUT is the output resistance (in ohms) , V OUT(OC) is the open-circuit output voltage (in volts) and I OUT(SC) is the short-circuit output current (in amps).  

14. 10/12/2023 Dept. of ECE, NIE Mysuru 14 Operational amplifiers Input offset voltage An ideal operational amplifier would provide zero output voltage when 0V difference is applied to its inputs. In practice, due to imperfect internal balance , there may be some small voltage present at the output . The voltage that must be applied differentially to the operational amplifier input in order to make the output voltage exactly zero is known as the input offset voltage . Input offset voltage may be minimized by applying relatively large amounts of negative feedback or by using the offset null facility provided by a number of operational amplifier devices. Typical values of input offset voltage range from 1 mV to 15 mV .

15. 10/12/2023 Dept. of ECE, NIE Mysuru 15 Operational amplifiers Full-power bandwidth The full-power bandwidth for an operational amplifier is equivalent to the frequency at which the maximum undistorted peak output voltage swing falls to 0.707 of its low-frequency ( d.c. ) value. Typical full-power bandwidths range from 10 kHz to over 1 MHz for some high-speed devices. Slew rate The slew rate of an operational amplifier is the “ rate of change of output voltage with time in response to a perfect step-function input”. Slew Rate = where Δ V OUT is the change in output voltage (in volts) and Δ t is the corresponding interval of time (in seconds) . Slew rate is measured in V/s (or V/ μs ) and typical values range from 0.2 V/ μs to over 20 V/ μs .  

16. 10/12/2023 Dept. of ECE, NIE Mysuru 16 Operational amplifiers Slew rate Fig: Slew rate for an operational amplifier

17. 10/12/2023 Dept. of ECE, NIE Mysuru 17 Operational amplifiers Problem 3 A perfect rectangular pulse is applied to the input of an operational amplifier. If it takes 4 μs for the output voltage to change from –5 V to +5 V, determine the slew rate of the device. Solution: Slew Rate = Slew Rate = = 2.5V/µs  

18. 10/12/2023 Dept. of ECE, NIE Mysuru 18 Operational amplifiers Problem 4 A wideband operational amplifier has a slew rate of 15 V/ μs . If the amplifier is used in a circuit with a voltage gain of 20 and a perfect step input of 100 mV is applied to its input, determine the time taken for the output to change level. Solution: The output voltage change will be 20 × 100 = 2,000 mV (or 2 V) Slew Rate = = = 0.133µs  

19. Characteristics of ideal and practical op-amp 10/12/2023 Dept. of ECE, NIE Mysuru 19

20. Characteristics of ideal and practical op-amp 10/12/2023 Dept. of ECE, NIE Mysuru 20 Characteristics for an ‘ideal’ operational amplifier are: (a) The open-loop voltage gain should be very high (ideally infinite). (b) The input resistance should be very high (ideally infinite). (c) The output resistance should be very low (ideally zero). (d) Full-power bandwidth should be as wide as possible. (e) Slew rate should be as large as possible. (f) Input offset should be as small as possible.

21. Characteristics of ideal and practical op-amp 10/12/2023 Dept. of ECE, NIE Mysuru 21 Table: Comparison of operational amplifier parameters for ‘ideal’ and ‘real’ devices Parameter Ideal Real Voltage gain Infinite 100,000 Input resistance Infinite 100 M Ω Output resistance Zero 20 Ω Bandwidth Infinite 2 MHz Slew rate Infinite 10 V/ μ s Input offset Zero Less than 5 mV

22. Operational amplifier applications 10/12/2023 Dept. of ECE, NIE Mysuru 22 Table: Some common examples of integrated circuit operational amplifiers

23. Practical op- amp circuits 10/12/2023 Dept. of ECE, NIE Mysuru 23

24. Practical op- amp circuits 10/12/2023 Dept. of ECE, NIE Mysuru 24 The Inverting Op-Amp Circuit An inverting opamp circuit is one whose output is out of phase by 180° w.r.t to the input.

25. Practical op- amp circuits 10/12/2023 Dept. of ECE, NIE Mysuru 25 The Inverting Op-Amp Circuit The current through R in is i = ----------------- (1) The potential V at G = 0 Because of the infinite input impedance of the op-amp, no current enters the op-amp. Hence the same current flows through the feedback resistor R f . Therefore, i = ------------------ (2) From equation (1) and (2), =  

26. Practical op- amp circuits 10/12/2023 Dept. of ECE, NIE Mysuru 26 The Inverting Op-Amp Circuit = = V out = - V i -------------(3) The ratio V o /V i is the closed loop voltage gain V CL of the circuit. The minus sign (-) in the equation (3) indicates that the output is INVERTED w.r.t input Thus the circuit is INVERTING OP-AMP.  

27. Practical op- amp circuits 10/12/2023 Dept. of ECE, NIE Mysuru 27 The Inverting Op-Amp Circuit

28. Practical op- amp circuits 10/12/2023 Dept. of ECE, NIE Mysuru 28 The Non-Inverting Op-Amp circuit A non inverting opamp circuit is one whose output is in phase w.r.t to the input.

29. Practical op- amp circuits 10/12/2023 Dept. of ECE, NIE Mysuru 29 The Non-Inverting Op-Amp Circuit The current through R in is i = ----------------- (1) The potential V at G = 0 Because of the infinite input impedance of the op-amp, no current enters the op-amp. Hence the same current flows through the feedback resistor R f . Therefore, i = ------------------ (2) From equation (1) and (2), =  

30. Practical op- amp circuits 10/12/2023 Dept. of ECE, NIE Mysuru 30 The Inverting Op-Amp Circuit = = - 1 = A V = = 1 + ------------(3) V out = V i (1 +  

31. Practical op- amp circuits 10/12/2023 Dept. of ECE, NIE Mysuru 31 The Non-Inverting Op-Amp circuit

32. Practical op- amp circuits APPLICATIONS 10/12/2023 Dept. of ECE, NIE Mysuru 32

33. Practical op- amp circuits APPLICATIONS 10/12/2023 Dept. of ECE, NIE Mysuru 33 The Voltage Follower Op-Amp Circuit An voltage follower opamp circuit is one whose output is in phase w.r.t to the input. The output voltage is equal to the input voltage . V o ≈ V i Fig: A voltage follower Fig: Typical input and output waveforms for a voltage follower

34. Practical op- amp circuits APPLICATIONS 10/12/2023 Dept. of ECE, NIE Mysuru 34 The Voltage Follower Op-Amp: Circuit

35. Practical op- amp circuits APPLICATIONS 10/12/2023 Dept. of ECE, NIE Mysuru 35 The Voltage Follower Op-Amp Circuit: Waveform

36. Practical op- amp circuits APPLICATIONS 10/12/2023 Dept. of ECE, NIE Mysuru 36 The Voltage Follower Op-Amp As the output voltage faithfully follows the input voltage at all instants, this op-amp is called “Voltage Follower”

37. Practical op- amp circuits APPLICATIONS 10/12/2023 Dept. of ECE, NIE Mysuru 37 The Summing Operational Amplifier Circuit

38. Practical op- amp circuits APPLICATIONS 10/12/2023 Dept. of ECE, NIE Mysuru 38 The Summing Operational Amplifier Circuit: Inverting Output

39. Practical op- amp circuits APPLICATIONS 10/12/2023 Dept. of ECE, NIE Mysuru 39 The Summing Operational Amplifier Circuit

40. Practical op- amp circuits APPLICATIONS 10/12/2023 Dept. of ECE, NIE Mysuru 40 The Summing Operational Amplifier Circuit: Non Inverting Output

41. Practical op- amp circuits APPLICATIONS 10/12/2023 Dept. of ECE, NIE Mysuru 41 The Subtractor/Difference Operational Amplifier Circuit

42. Practical op- amp circuits APPLICATIONS 10/12/2023 Dept. of ECE, NIE Mysuru 42 The Subtractor/Difference Operational Amplifier Circuit Output

43. Practical op- amp circuits APPLICATIONS 10/12/2023 Dept. of ECE, NIE Mysuru 43 The Differentiator Operational Amplifier Circuit A differentiator produces an output voltage that is equivalent to the rate of change of its input. Fig: A Differentiator

44. Practical op- amp circuits APPLICATIONS 10/12/2023 Dept. of ECE, NIE Mysuru 44 The Differentiator Operational Amplifier Circuit

45. Practical op- amp circuits APPLICATIONS 10/12/2023 Dept. of ECE, NIE Mysuru 45 The Differentiator Operational Amplifier Circuit Waveform

46. Practical op- amp circuits APPLICATIONS 10/12/2023 Dept. of ECE, NIE Mysuru 46 The Differentiator Operational Amplifier Circuit Waveform

47. Practical op- amp circuits APPLICATIONS 10/12/2023 Dept. of ECE, NIE Mysuru 47 The Differentiator Operational Amplifier Circuit Waveform

48. Practical op- amp circuits APPLICATIONS 10/12/2023 Dept. of ECE, NIE Mysuru 48 The Differentiator Operational Amplifier Circuit Waveform

49. Practical op- amp circuits APPLICATIONS 10/12/2023 Dept. of ECE, NIE Mysuru 49 The Integrator Operational Amplifier Circuit An Integrator circuit is one whose output is the integral of the input. Fig: An Integrator

50. Practical op- amp circuits APPLICATIONS 10/12/2023 Dept. of ECE, NIE Mysuru 50 The Integrator Operational Amplifier Circuit

51. Practical op- amp circuits APPLICATIONS 10/12/2023 Dept. of ECE, NIE Mysuru 51 The Integrator Operational Amplifier Circuit Waveform

52. Practical op- amp circuits APPLICATIONS 10/12/2023 Dept. of ECE, NIE Mysuru 52 The Integrator Operational Amplifier Circuit Waveform

53. Practical op- amp circuits APPLICATIONS 10/12/2023 Dept. of ECE, NIE Mysuru 53 The Integrator Operational Amplifier Circuit Waveform

54. OSCILLATORS 10/12/2023 Dept. of ECE, NIE Mysuru 54

55. OSCILLATORS 10/12/2023 Dept. of ECE, NIE Mysuru 55 Introduction to Oscillators An oscillator is a circuit which produces a continuous, repeated, alternating waveform without any input. Oscillators basically convert unidirectional current flow from a DC source into an alternating waveform which is of the desired frequency, as decided by its circuit components. The basic principle behind the working of oscillators can be understood by analyzing the behavior of an LC tank circuit .

56. OSCILLATORS 10/12/2023 Dept. of ECE, NIE Mysuru 56 Introduction to Oscillators Here, at first, the capacitor starts to discharge via the inductor, which results in the conversion of its electrical energy into the electromagnetic field, which can be stored in the inductor. Once the capacitor discharges completely, there will be no current flow in the circuit.

57. OSCILLATORS 10/12/2023 Dept. of ECE, NIE Mysuru 57 Introduction to Oscillators Then, the stored electromagnetic field would have generated a back-emf which results in the flow of current through the circuit in the same direction as that of before. This current flow through the circuit continues until the electromagnetic field collapses which result in the back-conversion of electromagnetic energy into electrical form, causing the cycle to repeat. However, now the capacitor would have charged with the opposite polarity, due to which one gets an oscillating waveform as the output.

58. OSCILLATORS 10/12/2023 Dept. of ECE, NIE Mysuru 58 Introduction to Oscillators

59. OSCILLATORS 10/12/2023 Dept. of ECE, NIE Mysuru 59 Introduction to Oscillators Fig: Decreased Oscillations Fig: Increased Oscillations Fig: Constant Oscillations

60. OSCILLATORS 10/12/2023 Dept. of ECE, NIE Mysuru 60 Types of Oscillators Wien Bridge Oscillator RC Phase Shift Oscillator Hartley Oscillator Voltage Controlled Oscillator Colpitts Oscillator Clapp Oscillators Crystal Oscillators Armstrong Oscillator Tuned Collector Oscillator Gunn Oscillator Cross-Coupled Oscillators Ring Oscillators Dynatron Oscillators Meissner Oscillators Opto-Electronic Oscillators Pierce Oscillators Robinson Oscillators Tri- tet Oscillators Pearson-Anson Oscillators Delay-Line Oscillators Royer Oscillators Electron Coupled Oscillators Multi-Wave Oscillators

61. OSCILLATORS 10/12/2023 Dept. of ECE, NIE Mysuru 61 Crystal controlled oscillators Whenever an oscillator is under continuous operation, its frequency stability gets affected. There occur changes in its frequency. The main factors that affect the frequency of an oscillator are Power supply variations Changes in temperature Changes in load or output resistance In RC and LC oscillators the values of resistance, capacitance and inductance vary with temperature and hence the frequency gets affected. In order to avoid this problem, the piezo electric crystals are being used in oscillators. The use of piezo electric crystals in parallel resonant circuits provide high frequency stability in oscillators. Such oscillators are called as Crystal Oscillators .

62. OSCILLATORS 10/12/2023 Dept. of ECE, NIE Mysuru 62 Crystal controlled oscillators The principle of crystal oscillators depends upon the Piezo electric effect . The crystal exhibits the property that when a mechanical stress is applied across one of the faces of the crystal, a potential difference is developed across the opposite faces of the crystal. Conversely, when a potential difference is applied across one of the faces, a mechanical stress is produced along the other faces. This is known as Piezo electric effect . Certain crystalline materials like Rochelle salt, quartz and tourmaline exhibit piezo electric effect and such materials are called as Piezo electric crystals . Quartz is the most commonly used piezo electric crystal because it is inexpensive and readily available in nature.

63. OSCILLATORS 10/12/2023 Dept. of ECE, NIE Mysuru 63 Crystal controlled oscillators When a piezo electric crystal is subjected to a proper alternating potential, it vibrates mechanically. The amplitude of mechanical vibrations becomes maximum when the frequency of alternating voltage is equal to the natural frequency of the crystal. Working of a Quartz Crystal

64. OSCILLATORS 10/12/2023 Dept. of ECE, NIE Mysuru 64 Crystal controlled oscillators

65. 10/12/2023 Dept. of ECE, NIE Mysuru 65 Thank You