LINEAR INTEGRATED CIRCUITS UNIT 1 LINEAR AND DIGITAL IC

LINEAR ICs

1. Malla Reddy College of Engineering and Technology (Autonomous Institution – UGC, Govt. of India) Department of ECE Presented by Dr.V.M.Senthilkumar Professor/ECE/MRCET LINEAR AND DIGITAL IC

2. Course Objectives & Outcomes Prerequisite: Electronic Devices and Circuits Switch Theory and Logic Design COURSE OBJECTIVES: COURSE OUTCOMES: Malla Reddy College of Engineering and Technology 2 1. To study the basic building blocks of linear integrated circuits. 2. To design the linear and non-linear applications of operational amplifiers. 3. To analyze the theory of ADC and DAC. 4. To introduce the concepts of waveform generation and introduce some special function ICs. 5. To understand and implement the working of basic digital circuits. On completion of this course, the students will have: 1. A thorough understanding of operational amplifiers with linear integrated circuits. 2. Understanding of the different families of digital integrated circuits and their characteristics. 3. To design circuits using operational amplifiers for various applications

3. Course Contents Unit 1 - Operational Amplifier Unit 2 - OP-Amp,IC555 & IC565 Applications Unit 3 - Data Converters Unit 4 - Digital Integrated circuits Unit 5 - Sequential Logic IC’s & Memories Malla Reddy College of Engineering and Technology 3

4. III Year B.Tech ECE-I Sem ( R18A0409) LINEAR & DIGITAL IC UNIT – I: Operational Amplifier: Ideal and Practical Op-Amp, Op-Amp Characteristics, DC and AC Characteristics , Features of 741 Op-Amp, Modes of Operation – Inverting, Non-Inverting, Differential, Instrumentation Amplifier, AC Amplifier, Differentiators and Integrators, Comparators , Schmitt Trigger, Introduction to Voltage Regulators, Features of 723 Regulator, Three Terminal Voltage Regulators . UNIT – II: Op-Amp, IC-555 & IC 565 Applications: Introduction to Active Filters, Characteristics of Band pass , Band reject and All Pass Filters, Analysis of 1st order LPF & HPF Butterworth Filters, waveform Generators – Triangular, Saw tooth, Square wave, IC555 Timer – Functional Diagram, Monostable and Astable Operations, Applications, IC565 PLL – Block Schematic, Description of Individual Blocks, Applications. UNIT – III: Data Converters: Introduction, Basic DAC techniques, Different types of DACs-Weighted resistor DAC, R-2R ladder DAC, Inverted R-2R DAC, Different Types of ADCs – Parallel Comparator Type ADC, Counter Type ADC, Successive Approximation ADC and Dual Slope ADC,DAC and ADC Specifications. Malla Reddy College of Engineering and Technology 4

5. Contd … UNIT – IV: Digital Integrated Circuits: Classification of Integrated Circuits, Comparison of Various Logic Families , CMOS Transmission Gate, IC interfacing. TTL Driving CMOS & CMOS Driving TTL, Combinational Logic ICs – Specifications and Applications of TTL-74XX & CMOS 40XX Series ICs – Code Converters, Decoders, Demultiplexers , LED & LCD Decoders with Drivers, Encoders, Priority Encoders, Multiplexers, Demultiplexers , Priority Generators/Checkers, Parallel Binary Adder / Subtractor , Magnitude Comparators . UNIT – V: Sequential Logic IC’s and Memories: Familiarity with commonly available 74XX & CMOS 40XX Series ICs – All Types of Flip-flops, Synchronous Counters, Decade Counters, Shift Registers. Memories – ROM Architecture, Types of ROMS & Applications, RAM Architecture, Static & Dynamic RAMs.   Malla Reddy College of Engineering and Technology 5

6. Text Books Malla Reddy College of Engineering and Technology 6 1.Linear Integrated Circuits – D.Roy Chowdhury , New Age International (p) Ltd, 2 nd Edition,2003 . 2. Op-Amps & Linear ICs - Ramakanth A. Gayakwad , PHI, 2003. 3.Digital fundamentals – Floyd and Jain, Pearson Education , 8th Edition ,2005.

7. HISTORY OF IC Malla Reddy College of Engineering and Technology 7 First op amps built in 1930’s-1940’s Used in WW-II to help how to strike military targets - Buffers, summers, differentiators, inverter

8. Contd … Vacuum Tube Era, 19 45 s 1 st used in Analog Computers Addition Subtraction Integration Differentiation Heavy Prone to failure K2-W tubes general purpose Op-Amp. 1952 8 Analog Computer

9. Contd.. In 1947 Bardeen and Brattain and Shockley succeeded in creating an amplifying circuit utilizing a point-contact " transfer resistance " device that later became known as a transistor. In 1951 Shockley developed the junction transistor, a more practical form of the transistor. By 1954 the transistor was an essential component of the telephone system and the transistor first appeared in hearing aids followed by radios . 1962 NPN Transistor 1963 RTL Logic 1965 - Moore’s Law, Transistors per IC doubles every 18 months - 2300 transistors on the 4004 (‘71) -> 42 Million on the Pentium 4 (’00), 2.3x1098 core Xenon Shrink Transistor Size by 30% every two years! Malla Reddy College of Engineering and Technology 9

10. Contd.. Malla Reddy College of Engineering and Technology 10 1967 MOS Transistor 1972 CMOS- INTEL 8008 1995 Intel Pentium Pro In 2000 Jack St. Clair Kilby was an American electrical engineer who took part (along with Robert Noyce ) in the realization of the first integrated circuit while working at Texas Instruments (TI) in 1958. He was awarded the Nobel Prize in Physics on December 10, 2000 .

11. Contd.. 2010-FinFET Device 2015-CNTFET 2018-SoC Malla Reddy College of Engineering and Technology 11

12. INTRODUCTION Integrated Circuit(IC)? -Microchip Why IC? - Size, Speed, Power & Complexity Malla Reddy College of Engineering and Technology 12

13. Classification of ICs Malla Reddy College of Engineering and Technology 13

14. Evolution of ICs Malla Reddy College of Engineering and Technology 14

15. Temperature Ranges Malla Reddy College of Engineering and Technology 15 Military temperature range : -55 o C to +125 o C (-55 o C to +85 o C) Industrial temperature range : -20 o C to +85 o C (-40 o C to +85 o C ) Commercial temperature range: 0 o C to +70 o C (0 o C to +75 o C )

16. Advantages Small size Low cost Less weight Low supply voltages Low power consumption Highly reliable Matched devices Fast speed Malla Reddy College of Engineering and Technology 16

17. D isadvantages Integrated circuit (IC) can be handle only limited amount of power. It is difficult to be achieved low temperature coefficient. The coils or inductors cannot be fabricated. Low noise and high voltage operation are not easily obtained. Power dissipation is limited to 10 watts Malla Reddy College of Engineering and Technology 17

18. Operational amplifier Circuit symbol. Operational Amplifiers picture. Pin Diagram. Important terms and equation. Ideal op-amp. Non ideal op-amp . Characteristics of op-amp. Application . Advantages & disadvantages. Conclusion . CONTENT S

19. UNIT-1-Operational Amplifier The term “operational amplifier” denotes a special type of amplifier that, by proper selection of its external components , could be configured for a variety of operations. Eg.IC 741 The number 741 indicates that this operational amplifier IC has 7 functional pins, 4 pins capable of taking input and 1 output pin . HISTORY First developed by John R. Ragazine in 1947 with vacuum tube. In 1960 at FAIRCHILD SEMICONDUCTOR CORPORATION, Robert J.Widlar fabricated op amp with the help of IC fabrication technology . In 1968 FAIRCHILD introduces the op-amp that was to become the industry standard. Malla Reddy College of Engineering and Technology 19

20. Contd … An operational amplifier (op-amp) is a DC-coupled high-gain electronic voltage amplifier, Direct- coupled high gain amplifier usually consisting of one or more differential amplifiers Output stage is generally a push-pull or push-pull complementary-symmetry pair. Malla Reddy College of Engineering and Technology 20

21. Fig.. Ckt symbol for general purpose op-amp Figure shows the symbol of op-amp & the power supply connections to make it work. The input terminal identified by the ‘-’ and “+” symbols are designated inverting & non- inverting. Their voltage w.r.t ground are denoted as V N & V P and output voltage as V O . Op- amp do not have a zero volt ground terminal Ground reference is established externally by the power supply common.

22. Operational Amplifiers picture Figure: The Philbrick Operational Amplifier. Figure : What an Op-Amp looks like in today's world

23. Op-amp pin diagram There are 8 pins in a common Op-Amp, like the 741 which is used in many instructional courses. Pin 1: Offset null Pin 2: Inverting input terminal Pin 3: Non-inverting input terminal Pin 4: –VCC (negative voltage supply) Pin 5: Offset null Pin 6: Output voltage Pin 7: +VCC (positive voltage supply) Pin 8: No Connection Figure : Pin connection, LM741.

24. V d V N V p V a = gain of amplifiers. V d= difference between the voltage. V 0= gain of voltage. The equation : V = a (V P -V N ) Electrical parameter : Input bias current(I b ): average of current that flows into the inverting and non-inverting input terminal of op-amp. I/p and o/p impedance: It is the resistance offered by the inputs and the output terminals to varying voltages. The quantity is expressed in Ohms. Open Loop Gain: It is the overall voltage gain or the amplification. Input offset voltage : It is a voltage that must be applied between the two terminal of an op-amp to null the o/p. Input offset current (I i ): The algebraic different between the current in to the inverting and Non-inverting terminal. Important terms and equation

25. IDEAL OP-AMP i N We know to minimize loading , a well designed voltage amplifier must draw negligible current from the input source and must present negligible resistance t o the output load . Op-amp are no V O e x cept i o n s o w e d e fin e the ideal o p - amp i p as an ideal voltage amplifier with infinite open loop gain. Infinity Its ideal terminal condition are r d = infinity ,r o = 0,i p = i n = 2

26. IDEAL OP-AMP PROPERT Y Infinite voltage gain Infinite input resistance rd so that almost any signal source can drive it and there is no loading of the preceding stage. Zero output resistance ro so that the output can drive an infinite number of other device . Zero output voltage when input is zero. Infinite common mode rejection ratio so that the output common mode noise voltage is zero. Infinite slew rate so that output voltage changes occurs simultaneously with input voltage changes. 3

27. Non -ideal op-amp This is opposite to the ideal op-amp only the positive and Negative terminal are change there position. There is a single external input signal V1=V+ that is applied to the +Ve pin of op-amp. A signal is also made to appear at the -Ve input terminal, But this is derived from resistors R1 and R2. V 1= V +

28. CHARACTERISTICS OF IDEAL OP-AMP Infinite input impedance(about 2Mohm) Low output impedance(about 200 ohm) Very large voltage gain at low frequency Infinite bandwidth(all frequencies are amplified by same factor Infinite Common-mode rejection ratio Infinite Power supply rejection ratio.

29. Characteristics of N on ideal op-amp Finite open-loop gain that causes gain error Finite input impedance Non zero output impedance Finite CMRR Common-mode input resistance Finite bandwidth Finite power supply rejection ratio.

30. Applications A to D Converters Power source Zero Crossing Detector (ZCD) Malla Reddy College of Engineering and Technology 30

31. A D V AN T A G E S O F AN O P - AM P : - Op-Amp. is an universal amplifier. Voltage comparators. Precision rectifiers. Analog to digital converters. Digital to analog converters. Filters. Differentiators and integrators. Voltage and current regulator. Analog to computers.

32. Block Diagram of Op-Amplifier

33. Ideal Voltage transfer curve +V sat -V sat +V d -V d A OL = ∞ + V sat ≈ +V cc

34. Practical Op-Amplifier The open loop gain of practical Op – Amp is around 7000. Practical Op – Amp has non zero offset voltage. That is, the zero output is obtained for the non – zero differential input voltage only. The bandwidth of practical Op – Amp is very small value. This can be increased to desired value by applying an adequate negative feedback to the Op – Amp. The output impedance is in the order of hundreds. This can be minimized by applying an adequate negative feedback to the Op – Amp. The input impedance is in the order of Mega Ohms only. (Whereas the ideal Op – Amp has infinite input impedance).

35. Differences between Ideal and practical Op-Amps

36. Op-amp Characteristics DC Characteristics Input bias current Input offset current Input offset voltage Thermal drift AC Characteristics Slew rate Frequency response

37. DC Characteristics The non ideal dc characteristics that add error components to the dc output voltage are, Input Bias Current Input Offset Current Input offset Voltage Total Output offset Voltage Thermal drift

38. Input Bias Current In an ideal op-amp, we assumed that no current is drawn from the input terminals. The base currents entering into the inverting and non-inverting terminals ( I B + & I B - respectively). Input bias current IB is the average value of the base currents entering into terminal of an op-amp

39. Input Bias Current The effect can be compensated with compensation resistor R comp . By KVL,Vo = V2 – V1 By selecting proper value of Rcomp , V2 can be cancelled with V1 and the Vo = 0. The value of Rcomp is derived as,

40. Input Bias Current

41. Input offset current The difference between the bias currents at the input terminals of the op- amp is called as input offset current. The input terminals conduct a small value of dc current to bias the input transistors. Since the input transistors cannot be made identical, there exists a difference in bias currents Even with bias current compensation, offset current will produce an output voltage when Vi = 0. V 1 = I B + Rcomp I 1 = V 1 /R 1

42. Input offset current So even with bias current compensation and with feedback resistor of 1M, a BJT op-amp has an output offset voltage Vo = 1M Ω X 200nA Vo = 200mV with Vi = 0

43. Input offset current T-feed back network is a good solution Provides a feedback signal as if the network were a single feedback resistor By T to π conversion,

44. Input offset voltage A small voltage applied to the input terminals to make the output voltage as zero when the two input terminals are grounded is called input offset voltage, Vos

45. Input offset voltage Let us determine the Vos on the output of inverting and non-inverting amplifier. If Vi = 0 (Fig (b) and (c)) become the same as in figure (d). V 2 at the – ve input terminal is given by,

46. Total Output Offset Voltage The maximum offset voltage at the output of an inverting and non-inverting amplifier without any compensation technique used is given by With Rcomp in the circuit, total output offset voltage will be given by

47. 47 THERMAL DRIFT Bias current, offset current and offset voltage change with temperature. A circuit carefully nulled at 25 o c may not remain so when the temperature rises to 35 o c. This is called drift. Offset current drift is expressed in nA /ºC. Offset voltage drift is expressed in mV/ºC. Indicates the change in offset for each degree celsius change in temperature

48. AC Characteristics Frequency Response Ideally, an op-amp should have an infinite bandwidth but practically op-amp gain decreases at higher frequencies. Such a gain reduction with respect to frequency is called as roll off. The plot showing the variations in magnitude and phase angle of the gain due to the change in frequency is called frequency response of the op-amp

49. When the gain in decibels, phase angle in degrees are plotted against logarithmic scale of frequency, the plot is called Bode Plot The manner in which the gain of the op-amp changes with variation in frequency is known as the magnitude plot . The manner in which the phase shift changes with variation in frequency is known as the phase-angle plot .

50. Obtaining the frequency response To obtain the frequency response , consider the high frequency model of the op-amp with capacitor C at the output, taking into account the capacitive effect present Where A OL (f) = open loop voltage gain as a function of frequency A OL = Gain of the op-amp at 0Hz F = operating frequency F o = Break frequency or cutoff frequency of op-amp

51. For a given op-amp and selected value of C, the frequency f o is constant. The above equation can be written in the polar form as

52. Frequency Response of an op-amp

53. The following observations can be made from the frequency response of an op-amp The open loop gain A OL is almost constant from 0 Hz to the break frequency f o . At f= f o , the gain is 3dB down from its value at 0Hz . Hence the frequency f o is also called as -3dB frequency. It is also know as corner frequency After f= f o , the gain A OL (f) decreases at a rate of 20 dB/decade or 6dB/octave. As the gain decreases, slope of the magnitude plot is -20dB/decade or -6dB/octave, after f= f o . At a certain frequency, the gain reduces to 0dB. This means 20log|A OL | is 0dB i.e. |A OL | =1. Such a frequency is called gain cross-over frequency or unity gain bandwidth (UGB). It is also called closed loop bandwidth. UGB is the gain bandwidth product only if an op-amp has a single breakover frequency, before A OL (f) dB is zero.

54. For an op-amp with single break frequency f o , after f o the gain bandwidth product is constant equal to UGB UGB=A OL f o UGB is also called gain bandwidth product and denoted as f t Thus f t is the product of gain of op-amp and bandwidth. The break frequency is nothing but a corner frequency f o . At this frequency, slope of the magnitude plot changes. The op-amp for which there is only once change in the slope of the magnitude plot, is called single break frequency op-amp.

55. For a single break frequency we can also write UGB= A f f f A f = closed loop voltage gain F f = bandwidth with feedback v) The phase angle of an op-amp with single break frequency varies between 0 to 90 . The maximum possible phase shift is -90 , i.e. output voltage lags input voltage by 90 when phase shift is maximum vi) At a corner frequency f=f o , the phase shift is -45 0. F o = UGB / A OL

56. OPERATIONAL AMPLIFIERS AC CHARACTERISTICS

57. AC Characteristics Frequency Response Ideally, an op-amp should have an infinite bandwidth but practically op-amp gain decreases at higher frequencies. Such a gain reduction with respect to frequency is called as roll off. The plot showing the variations in magnitude and phase angle of the gain due to the change in frequency is called frequency response of the op-amp

58. When the gain in decibels, phase angle in degrees are plotted against logarithmic scale of frequency, the plot is called Bode Plot The manner in which the gain of the op-amp changes with variation in frequency is known as the magnitude plot . The manner in which the phase shift changes with variation in frequency is known as the phase-angle plot .

59. Frequency Response Ideal Op-Amp will have Infinite Gain In general, open loop gain is 90dB with dc signal What should be the expected gain for audio and other high frequency signal? Must be same, but practically it is not possible Op-Amp gain decreases (or roll-off) at higher frequencies What Causes the gain of the op-amp to roll off? Presence of capacitive component !!! Internal construction of op-amp & physical characteristics of the device

60. High frequency Model of the Op-Amp HF model of the op-amp with only one corner frequency One pole due to R o C & -20dB/decade roll-off

61. The open loop gain of the op-amp with only one corner frequency is Where f 1 is the corner frequency or the upper 3-dB frequency of the op-amp.

62. From the magnitude & phase characteristics, it can be seen that for f << f 1 , the magnitude of the gain is 20 log A OL in dB for f = f 1 , the gain is 3dB down from the dc value of A OL , called corner frequency. for f >> f 1 , the gain rolls-off at the rate of -20 dB/decade or – 6 db/octave.

63. From the phase characteristics Phase angle is zero at f = 0 At f 1, the phase angle is -45 o (lagging) and Infinite frequencies, the phase angle is -90 o . For single RC pair, maximum phase change of 90 o can occur. The voltage transfer function in s-domain can be written as

64. For number of stages or RC pole pairs, there will be number of corner frequencies

65. Stability of Op-Amp What is the effect of feedback on op-amp? Resistor in the feedback part of the op-amp For inverting amplifier, 180 o phase shift in the output, at low frequencies

66. The closed loop transfer function is A cL = A / (1 + A β ) If the characteristic equation (1 + A β )=0, circuit will become unstable, (i.e.) it leads to sustained oscillation Re-writing the characteristic equation as (1 –(-A β ))=0 leads to –A β =1 Magnitude and Phase condition becomes |A β |=1 and

67. At low frequencies, the resistor in the feedback has no effect, except producing 180 deg. Phase shift. However, at high frequencies, for each corner frequencies , an additional phase shift of maximum -90 o can take place in open loop gain A. For two corner frequencies, it will be -180 deg. For a specific value of β , A β = 1, when A is -180 deg. This results in oscillation and this instability means unbounded output. (1 + A β ) < 1 (or) A β < 0 & A cL > A

68. Slew rate It is defined as the maximum rate of change of output voltage caused by a step input voltage. The slew rate is specified in V/ µsec Slew rate = S = dV o / dt | max It is specified by the op-amp in unity gain condition. The slew rate is caused due to limited charging rate of the compensation capacitor and current limiting and saturation of the internal stages of op-amp, when a high frequency large amplitude signal is applied.

69. Slew rate It is given by dV c /dt = I/C For large charging rate, the capacitor should be small or the current should be large. S = I max / C For 741 IC the charging current is 15 µA and the internal capacitor is 30 pF. S= 0.5V/ µsec Slew rate limits the response speed of all large signal wave shapes.

70. Slew rate equation V s = V m sin ω t V o = V m sin ω t S =slew rate = = V m ω cos ω t max S = V m ω = 2 π f V m S = 2 π f V m V / sec For distortion free output, the maximum allowable input frequency f m can be obtained as This is also called full power bandwidth of the op-amp

71. Features of 741 Op-Amp The IC 741 is high performance monolithic op-amp IC.It is available in 8pin, 10pin or 14pin configuration. It can operate over a temperature of -55 C to 125 C. Features: No frequency compensation required Short circuit protection provided Offset Voltage null capability Large common mode and differential voltage range No latch up It consumes low power

72. Internal schematic of 741 op-amp

73. 8pin DIP package of IC 741

74. M odes of Operation using an op-amp Open Loop : The output assumes one of the two possible output states, that is +V sat or – V sat and the amplifier acts as a switch only. Closed Loop : The utility of an op-amp can be greatly increased by providing negative feed back. The output in this case is not driven into saturation and the circuit behaves in a linear manner.

75. Open loop op-amp configurations The configuration in which output depends on input, but output has no effect on the input is called open loop configuration. No feed back from output to input is used in such configuration. The op-amp can be used in three modes in open loop configuration they are Differential amplifier Inverting amplifier Non inverting amplifier

76. Differential Amplifier The amplifier which amplifies the difference between the two input voltages is called differential amplifier. V o  A OL V d  A OL ( V 1  V 2 )  A OL ( V in 1  V in 2 ) Key point: For very small V d , output gets driven into saturation due to high A OL , hence this application is applicable for very small range of differential input voltage.

77. Inverting Amplifier The amplifier in which the output is inverted i.e. having 180 o phase shift with respect to the input is called an inverting amplifier V o = -A OL V in2 Keypoint: The negative sign indicates that there is phase shift of 180 o between input and output i.e. output is inverted with respect to input.

78. Non-inverting Amplifier The amplifier in which the output is amplified without any phase shift in between input and output is called non inverting amplifier V o = A OL V in1 Keypoint: The positive output shows that input and output are in phase and input is amplified A OL times to get the output.

79. Why op-amp is generally not used in open loop mode? As open loop gain of op-amp is very large, very small input voltage drives the op-amp voltage to the saturation level. Thus in open loop configuration, the output is at its positive saturation voltage (+V sat ) or negative saturation voltage (-V sat ) depending on which input V 1 or V 2 is more than the other. For a.c. input voltages, output may switch between positive and negative saturation voltages

80. Realistic simplifying assumptions Zero input current : The current drawn by either of the input terminals (inverting and non-inverting) is zero Virtual ground :This means the differential input voltage V d between the non-inverting and inverting terminals is essentially zero. (The voltage at the non inverting input terminal of an op-amp can be realistically assumed to be equal to the voltage at the inverting input terminal )

81. Closed loop operation of op-amp The closed loop operation is possible with the help of feedback. The feedback allows to feed some part of the output back to the input terminals. In the linear applications, the op- amp is always used with negative feedback. The negative feedback helps in controlling gain, which otherwise drives the op-amp out of its linear range, even for a small noise voltage at the input terminals

82. Inverting Amplifier In an inverting amplifier circuit, the operational amplifier inverting input receives feedback from the output of the amplifier.

83. Contd …

84. Non-Inverting Amplifier If the signal is applied to the non-inverting input terminal and feedback is given as shown in fig, the circuit amplifies without inverting the input signal. Such a circuit is called non-inverting amplifier. Negative feed back system as output is being fed back to the inverting input terminal.

85. Contd … 1. The voltage gain is always greater than one 2. 3. The voltage gain is positive indicating that for a.c . input, the output and input are in phase while for d.c . input, the output polarity is same as that of input The voltage gain is independent of open loop gain of op-amp, but depends only on the two resistance values 4. The desired voltage gain can be obtained by selecting proper values of R f and R 1

86. Comparison of the ideal inverting and non- inverting op-amp Ideal Inverting amplifier Ideal non-inverting amplifier 1. Voltage gain=- R f /R 1 1. Voltage gain=1+R f /R 1 2. The output is inverted with respect to input 2. No phase shift between input and output 3. The voltage gain can be adjusted as greater than, equal to or less than one 3. The voltage gain is always greater than one 4. The value of input impedance R1 should be kept fairly large to avoid loading effect. 4. The input impedance is very large

87. Differential Amplifier

88. Contd …

89. Difference mode and Common Mode Gains The output voltage depends on difference voltage (v d ) and average voltage of input signals called as common mode ( v CM ) signals. ----(1) ---(2) The output voltage is expressed as

90. Contd … (2)

91. Contd …

92. Instrumentation Amplifier An instrumentation amplifier is a type of differential amplifier that has been outfitted with input buffers, which eliminate the need for input impedance matching and thus make the amplifier particularly suitable for use in measurement and test equipment. In a number of industrial and consumer applications, the measurement of physical quantities is usually done with the help of transducers. The output of transducer has to be amplified So that it can drive the indicator or display system. This function is performed by an instrumentation amplifier

93. Block Diagram

94. Contd … The op-amps 1 & 2 are non-inverting amplifiers and op-amp 3 is a difference amplifier. These three op-amps together, form an instrumentation amplifier. Instrumentation amplifier’s final output Vout is the amplified difference of the input signals applied to the input terminals of op-amp 3.

95. Let the outputs of op-amp 1 and op-amp 2 be Vo1 and Vo2 respectively. Then, Vout = (R3/R2)(Vo1-Vo2) The working of the instrumentation amplifier is, Ideally the current to the input stage op-amps is zero. Therefore the current I through the resistors R1, Rgain , and R1 remain the same. Applying Ohm’s law between nodes I = (Vo1-o2)/(R1+R gain +R1)….(1) I = (Vo1-Vo2)/(2R1+R gain ) Since no current is flowing to the input of the op-amps 1 & 2, the current I between the nodes G and H can be given as, I = (V G -V H ) / R gain = (V 1 -V 2 ) / R gain ……………………….(2)

96. Contd … Equating equations 1 and 2, (Vo1-Vo2)/(2R1+Rgain) = (V1-V2)/ Rgain (Vo1-Vo2) = (2R1+Rgain)(V1-V2)/ Rgain ……………………….(3) The output of the difference amplifier is given as, Vout = (R3/R2) (Vo1-Vo2) Therefore, (Vo1 – Vo2) = (R2/R3) Vout Substituting (Vo1 – Vo2) value in equation 3, we get (R2/R3) Vout = (2R1+Rgain)(V1-V2)/ Rgain i.e. Vout = (R3/R2){(2R1+Rgain)/ Rgain }(V1-V2) V out = (R3/R2){(1+2R1/ R gain )}(V1-V2) The overall voltage gain of an instrumentation amplifier can be controlled by adjusting the value of resistor Rgain .

97. Features of instrumentation amplifier high gain accuracy high CMRR high gain stability with low temperature co efficient low dc offset low output impedance

98. Applications Instrumentation amplifiers are used in data acquisition from small o/p transducers like thermocouples , strain gauges, measurements of Wheatstone bridge , etc. used in navigation, medical, radar, etc. used to enhance the S/N ratio ( signal to noise ) in audio applications like audio signals with low amplitude. used for imaging as well as video data acquisition in the conditioning of high-speed signal. used in RF cable systems for amplification of the high-frequency signal.

99. AC Amplifiers To amplify a small AC input signal, such as an audio or radio frequency signal. A small AC voltage is applied to the input, through a coupling capacitor. ... (Hence, such a circuit is useful only as an AC amplifier; to amplify DC signals you should use an operational amplifier circuit). To get the ac frequency response of an op-amp or if the ac input signal is super imposed with dc level, it becomes essential to block the dc component. This is achieved by using an AC amplifier with a coupling capacitor. AC amplifiers are two types 1) Inverting AC ampr . 2) Non Inverting AC ampr .

100. Inverting AC Amplifier From the fig. The capacitor C blocks the dc component of the input and together with the resistor R1 sets the lower 3 db freq. of the ampr . The output vg. V =- IR f = V i R f /R 1 +1/ sC -----(1) -(2) ( -(3) -(4)

101. Non Inverting AC ampr .

102. Voltage Follower The circuit is used as a buffer to connect a high impedance signal sources to a low impedance load which may even be capacitive.

103. Integrator The circuit in which the output wave form is the integral of input wave form is known as an integrator. Such type of circuit is obtained by using basic inverting amplifier configuration where we use a capacitor in feed back

104. Circuit Diagram The Characteristic equation for a capacitor is ------(1) Input is applied to inverting terminal of the op-amp.  Non inverting terminal is grounded.  If sin wave is applied terminal then the output will be cosine wave.

105. Contd … ------(2) -----(3) -------(4) -

106. Contd … 2&4 ----(5) Combining Equa.5&3 -----(6) The output of the integrator is the integral of input voltage with time constant that is V is directly proportional to integral of V in dt and inversely proportional to the time constant. i

107. Response of a simple integrator

108. The input is sine wave the output become cosine wave Input Output Similarly the input is square wave the output become Triangle wave

109. Practical Integrator To reduce the error voltage at the output, a resistor R f is connected across the feed back capacitor C f .Thus R f limits the low frequency gain and minimizes the variations in the output voltage. The stability and low frequency roll-off problems can be corrected by the addition of a resistor R f

110. Frequency Response

111. Applications Integrators are commonly used as Analog computers A to D converters Many linear circuits Signal Wave Shaping circuit

112. Differentiator The differentiator is the circuit whose output wave form is the differential input wave form. The differentiator may be constructed form the basic inverting amplifier Here we replace the input resistor by a capacitor.

113. Frequency Response

114. Practical Differentiator Both the stability and the high frequency noise problems can be corrected by the addition of two components: R 1 and C f . f a = 1/2¶R f C 1 , f b =1/2¶R 1 C 1 Where f a is freq. at which the gain is 0 db, and f b is the gain limiting frequency. R 1 C 1 & R f C f to reduce significantly the effect of high frequency input, amplifier noise, and offsets.

115. Wave forms

116. Applications Wave shaping circuits to detect high frequency components in an input signal and also as a rate of change detector in FM modulators.

117. Comparators A comparator is a circuit which compares a signal voltage applied at one input of an op- amp with a known reference voltage at the other input. It is an open loop op - amp with output + Vsat . Types of Comparators 1.Non-Inverting comparator 2.Inverting Comparator

118. Non Inverting Comparator A fixed reference voltageV ref is applied to(-) input and a time varying signal v i is applied to (+) input.The output voltage is at – V sat for vi< V ref And v o goes to + V sat for vi> V ref .

119. Input & Output waveforms

120. Practical Non inverting Comparator

121. Inverting Comparator

122. Input & Output wave forms

123. Applications of Comparator 1.Zero crossing detector 2.Window detector 3.Time marker generator 4.Phase detector

124. Zero crossing Detector A zero crossing detector or ZCD is a voltage comparator, used to detect a sine waveform transition from positive and negative, that coincides when the i /p crosses the zero voltage condition

125. Window Detector

126. Schmitt Trigger Schmitt trigger is a regenerative comparator . It converts sinusoidal input into a square wave output. The output of Schmitt trigger swings between upper and lower threshold voltages, which are the reference voltages of the input waveform. The input voltage is applied to the (-) input terminal and feedback vg. to the(+) input terminal. The i /p vg. V i triggers the output v levels are called upper threshold voltage(V UT ) and lower threshold voltage(V LT ). The hysteresis width is the difference between these two threshold voltages i.e V UT - V LT

127. Contd … These threshold voltages are calculated as, The output v = +V sat . The voltage at(+) input terminal will be -----(1) For v = -V sat . The voltage at(+) input terminal will be ----(2)

128. Contd … V LT <V UT and the difference between these two voltages is the hysteresis width V H and can be written as - --(3) In the circuit of Fig.(a), V ref is chosen as zero volt, it follows equ . 1 and 2 that V UT = -V LT = R2V sat /R1+R2- ----(4) An input sinusoid of frequency f=1/T is applied to a comparator, a symmetrical square wave is obtained at the output.

129. Voltage Regulator

130. Outline Introduction Voltage Regulation Line Regulation Load Regulation Series Regulator IC Voltage Regulator

131. Introduction Batteries are often shown on a schematic diagram as the source of DC voltage but usually the actual DC voltage source is a power supply. There are many types of power supply. Most are designed to convert high voltage AC mains electricity to a suitable low voltage supply for electronics circuits and other devices. A more reliable method of obtaining DC power is to transform, rectify, filter and regulate an AC line voltage. A power supply can by broken down into a series of blocks, each of which performs a particular function.

132. Introduction Power supply : a group of circuits that convert the standard ac voltage (120 V, 60 Hz) provided by the wall outlet to constant dc voltage Transformer : a device that step up or step down the ac voltage provided by the wall outlet to a desired amplitude through the action of a magnetic field

133. Introduction Rectifier : a diode circuits that converts the ac input voltage to a pulsating dc voltage The pulsating dc voltage is only suitable to be used as a battery charger, but not good enough to be used as a dc power supply in a radio, stereo system, computer and so on.

134. Introduction There are two basic types of rectifier circuits: Half-wave rectifier Full-wave rectifier - Center-tapped & Bridge full-wave rectifier In summary, a full-wave rectified signal has less ripple than a half-wave rectified signal and is thus better to apply to a filter.

135. Introduction Filter : a circuit used to reduce the fluctuation in the rectified output voltage or ripple. This provides a steadier dc voltage. Regulator : a circuit used to produces a constant dc output voltage by reducing the ripple to negligible amount . One part of power supply.

136. Introduction Regulator - Zener diode regulator For low current power supplies - a simple voltage regulator can be made with a resistor and a zener diode connected in reverse. Zener diodes are rated by their breakdown voltage V z and maximum power P z (typically 400mW or 1.3W)

137. Voltage Regulation Two basic categories of voltage regulation are: line regulation load regulation The purpose of line regulation is to maintain a nearly constant output voltage when the input voltage varies. The purpose of load regulation is to maintain a nearly constant output voltage when the load varies

138. Line Regulation Line regulation: A change in input (line) voltage does not significantly affect the output voltage of a regulator (within certain limits)

139. Line Regulation Line regulation can be defined as the percentage change in the output voltage for a given change in the input voltage. Δ means “a change in” Line regulation can be calculated using the following formula:

140. Load Regulation Load regulation: A change in load current (due to a varying R L ) has practically no effect on the output voltage of a regulator (within certain limits)

141. Load Regulation Load regulation can be defined as the percentage change in the output voltage from no-load (NL) to full-load (FL). Where: V NL = the no-load output voltage V FL = the full-load output voltage

142. Load Regulation Sometimes power supply manufacturers specify the equivalent output resistance (R out ) instead of its load regulation. R FL equal the smallest-rated load resistance, then V FL :

143. Load Regulation Rearrange the equation:

144. Types of Regulator Fundamental classes of voltage regulators are linear regulators and switching regulators . Two basic types of linear regulator are the series regulator and the shunt regulator . The series regulator is connected in series with the load and the shunt regulator is connected in parallel with the load.

145. Series Regulator Circuit Control element in series with load between input and output. Output sample circuit senses a change in output voltage. Error detector compares sample voltage with reference voltage → causes control element to compensate in order to maintain a constant output voltage.

146. Op-Amp Series Regulator Control Element Error Detector Sample Circuit V REF

147. Op-Amp Series Regulator The resistor R 1 and R 2 sense a change in the output voltage and provide a feedback voltage. The error detector compares the feedback voltage with a Zener diode reference voltage. The resulting difference voltage causes the transistor Q 1 controls the conduction to compensate the variation of the output voltage. The output voltage will be maintained at a constant value of:

148. IC Voltage Regulators Regulation circuits in integrated circuit form are widely used. Their operation is no different but they are treated as a single device with associated components. These are generally three terminal devices that provide a positive or negative output. Some types have variable voltage outputs. A typical 7800 series voltage regulator is used for positive voltages. The 7900 series are negative voltage regulators. These voltage regulators when used with heatsinks can safely produce current values of 1A and greater. The capacitors act as line filtration.

149. IC Voltage Regulators Several types of both linear (series and shunt) and switching regulators are available in integrated circuit (IC) form. Single IC regulators contain the circuitry for: reference source comparator amplifier control device overload protection Generally, the linear regulators are three-terminal devices that provides either positive or negative output voltages that can be either fixed or adjustable.

150. Fixed Voltage Regulator The fixed voltage regulator has an unregulated dc input voltage V i applied to one input terminal, a regulated output dc voltage V o from a second terminal, and the third terminal connected to ground. Fixed-Positive Voltage Regulator The series 78XX regulators are the three-terminal devices that provide a fixed positive output voltage.

151. Fixed Voltage Regulator An unregulated input voltage V i is filtered by a capacitor C 1 and connected to the IC’s IN terminal. The IC’s OUT terminal provides a regulated +12 V, which is filtered by capacitor C 2 . The third IC terminal is connected to ground (GND)

152. Fixed Voltage Regulator IC Part Output Voltage (V) Minimum V i (V) 7805 +5 +7.3 7806 +6 +8.3 7808 +8 +10.5 7810 +10 +12.5 7812 +12 +14.5 7815 +15 +17.7 7818 +18 +21.0 7824 +24 +27.1 Positive-Voltage Regulators in the 78XX Series

153. Fixed Voltage Regulator Fixed-Negative Voltage Regulator The series 79XX regulators are the three-terminal IC regulators that provide a fixed negative output voltage. This series has the same features and characteristics as the series 78XX regulators except the pin numbers are different.

154. Fixed Voltage Regulator IC Part Output Voltage (V) Minimum V i (V) 7905 -5 -7.3 7906 -6 -8.4 7908 -8 -10.5 7909 -9 -11.5 7912 -12 -14.6 7915 -15 -17.7 7918 -18 -20.8 7924 -24 -27.1 Negative-Voltage Regulators in the 79XX Series

155. Fixed Voltage Regulator Adjustable-Voltage Regulator Voltage regulators are also available in circuit configurations that allow to set the output voltage to a desired regulated value. The LM317 is an example of an adjustable-voltage regulator, can be operated over the range of voltage from 1.2 to 37 V.

156. Features of 723 Regulators: It has wide variety of applications such as series, shunt, switching and floating regulators. Relative simplicity with power supply can be designed. It has small in size and lower in cost. Input voltage is maximum 40 V. Output voltage adjustable from 2 V to 37 V. Output current up to 150 mA without external pass transistor.

157. Contd… Load and line regulations of 0.03%. It operates in positive or negative supply operation. It has choice of supply voltage. Low standby current gain. Very low temperature drift and high ripple rejection. Built in fold back current limiting

158. 723 general purpose regulator

159. Summary Voltage regulators keep a constant dc output despite input voltage or load changes. The two basic categories of voltage regulators are linear and switching. The two types of linear voltage regulators are series and shunt. The three types of switching are step-up, step-down, and inverting.

160. Summary Switching regulators are more efficient than linear making them ideal for low voltage high current applications. IC regulators are available with fixed positive or negative output voltages or variable negative or positive output voltages. Both linear and switching type regulators are available in IC form. Current capacity of a voltage regulator can be increased with an external pass transistor.