Physics
Linear Op Amp
A linear operational amplifier (op-amp) is a type of electronic amplifier that produces an output that is proportional to the input signal. It is designed to have a linear response, meaning that the output varies in direct proportion to the input. Op-amps are commonly used in a wide range of electronic applications, including signal processing and control systems.
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eBook - PDF- Jiri Dostal(Author)
- 2013(Publication Date)
- Newnes(Publisher)
Parti The Operational Amplifier This page intentionally left blank 1. Basic Concepts 1.1 The Operational Amplifier The operational amplifier is a versatile amplifying device, originally intended for use in analog computers to perform linear mathematical operations. Forty years of development of the operational amplifier's internal circuit design reflects, to a significant extent, the development of electronic components from vacuum tubes to monolithic integrated circuits. An increasing refinement of the operational amplifier's properties has shifted the emphasis of its ap-plications from laboratories to industry. Due to its high performance, ver-satility, and low price, the operational amplifier now dominates the field of analog electronic systems. We generally define the operational amplifier as a direct-coupled amplifier with a high gain and a low level of inherent noise, capable of stable operation in a closed-feedback loop. The exact meaning of these characteristics will be given in Chapters 2 and 11. It should be mentioned here that the term direct-coupled does not imply an upper limitation of the amplifier's frequency re-sponse but, on the contrary, an extension of the operating range to zero frequency, or infinitely long periods. The direction of signal flow from input to output in an operational amplifier is given by the triangular shape of its symbol in Figure 1-la. Three of the four illustrated terminals represent the three signal terminals of an actual operational amplifier. These are the inverting input, noninverting input, and output. The fourth signal terminal, the ground, may be either actual (Figure 1—lb) or only virtual (power supply common in Figure 1-lc). In either case, it represents symbolically a group of at least two terminals intended for the supply of energy.
eBook - PDF- BRUCE NEWBY(Author)
- 2014(Publication Date)
- Butterworth-Heinemann(Publisher)
2 A review of operational amplifiers 2.1 Introduction In subsequent chapters of this book the operational amplifier plays a promi-nent part in the many signal conditioning circuits considered. For this reason alone, it is important that the reader is given a fairly comprehensive review of the techniques involved when using these very common devices in a signal conditioning role. The term operational amplifier or op-amp was originally used by workers in the analogue computing industry to describe electronic devices which would undertake a variety of mathematical operations. In simple terms, the devices were very high gain d.c. voltage amplifiers each fitted with a different feedback circuit between its output and input to produce a specific mathematical function. The functions obtainable included simple amplification, differentia-tion, integration, addition, subtraction and the like. Many of the functions undertaken by the early analogue computers have now become the province of the ubiquitous digital computer, causing a large decline in the numbers of the former. But the operational amplifier has not suffered the same fate; it has been retained and further developed and now is extensively used in the analogue electronics field of instrumentation. While operational amplifiers can be built from discrete components, the present proliferation of these devices has been largely brought about by their ready availability commercially in modular and integrated form. Many manufacturers now market a very wide range of high performance operational amplifiers which by the addition of a few simple external components can be configured to undertake specific signal processing tasks. Not only can they be designed to undertake the usual mathematical operations, but they can also be arranged to simulate, for example, the performance of a proposed mechanical, hydraulic or electrical control system.
eBook - PDF- Behzad Razavi(Author)
- 2021(Publication Date)
- Wiley(Publisher)
In this chapter, we study the operational amplifier as a black box, developing op-amp-based circuits that perform interesting and useful functions. The outline is shown below. 1 Vacuum tubes were amplifying devices consisting of a filament that released electrons, a plate that collected them, and another that controlled the flow—somewhat similar to MOSFETs. 355 356 Chapter 8 Operational Amplifier as a Black Box General Concepts • Op Amp Properties Linear Op Amp Circuits • Noninverting Amplifier • Inverting Amplifier • Integrator and Differentiator • Voltage Adder NonLinear Op Amp Circuits • Precision Rectifier • Logarithmic Amplifier • Square Root Circuit Op Amp Nonidealities • DC Offsets • Input Bias Currents • Speed Limitations • Finite Input and Output Impedances 8.1 GENERAL CONSIDERATIONS The operational amplifier can be abstracted as a black box having two inputs and one output. 2 Shown in Fig. 8.1(a), the op amp symbol distinguishes between the two inputs by the plus and minus sign; V in1 and V in2 are called the “noninverting” and “inverting” inputs, respectively. We view the op amp as a circuit that amplifies the difference between the two inputs, arriving at the equivalent circuit depicted in Fig. 8.1(b). The voltage gain is denoted by A 0 : V out = A 0 (V in1 − V in2 ). (8.1) We call A 0 the “open-loop” gain. V V in1 in2 out V in1 in2 A 0 V V in1 V ( V in2 – out V (a) (b) ) Figure 8.1 (a) Op amp symbol, (b) equivalent circuit. It is instructive to plot V out as a function of one input while the other remains at zero. With V in2 = 0, we have V out = A 0 V in1 , obtaining the behavior shown in Fig. 8.2(a). The positive slope (gain) is consistent with the label “noninverting” given to V in1 . On the other hand, if V in1 = 0, V out = −A 0 V in2 [Fig. 8.2(b)], revealing a negative slope and hence an “inverting” behavior.
eBook - PDF- Richard C. Dorf, James A. Svoboda(Authors)
- 2020(Publication Date)
- Wiley(Publisher)
6 The Operational Ampli fier Chapter Topics 6.1 Introduction 6.2 The Operational Amplifier 6.3 The Ideal Operational Amplifier 6.4 Nodal Analysis of Circuits Containing Ideal Operational Amplifiers 6.5 Design Using Operational Amplifiers 6.6 Operational Amplifier Circuits and Linear Algebraic Equations 6.7 Characteristics of Practical Operational Amplifiers 6.8 Analysis of Op Amp Circuits Using MATLAB 6.9 Using PSpice to Analyze Op Amp Circuits 6.10 How Can We Check . . . ? 6.11 DESIGN EXAMPLE— Transducer Interface Circuit 6.12 Summary Problems PSpice Problems Design Problems 6.1 I n t r o d u c t i o n This chapter introduces another circuit element, the operational amplifier, or op amp. We will learn how to analyze and design electric circuits that contain op amps. In particular, we will see that: Several models, of varying accuracy and complexity, are available for operational amplifiers. Simple models are easy to use. Accurate models are more complicated. The simplest model of the operational amplifier is the ideal operational amplifier. Circuits that contain ideal operational amplifiers are analyzed by writing and solving node equations. Operational amplifiers can be used to build circuits that perform mathematical operations. Many of these circuits are widely used and have been named. Figure 6.5-1 provides a catalog of some useful operational amplifier circuits. Practical operational amplifiers have properties that are not included in the ideal operational amplifier. These include the input offset voltage, bias current, dc gain, input resistance, and output resistance. More complicated models are needed to account for these properties. 6.2 T h e O p e r a t i o n a l A m p l i f i e r The operational amplifier is an electronic circuit element designed to be used with other circuit elements to perform a specified signal-processing operation. The mA741 operational amplifier is shown in Figure 6.2-1a.
eBook - PDF- Tim Williams(Author)
- 2013(Publication Date)
- Butterworth-Heinemann(Publisher)
The Circuit Designer's Companion Linear integrated circuits 135 The operational amplifier is the basic building block for analogue circuits, and progress in op-amp performance is the litmus test for linear IC technology in much the same way as progress in memory devices is for digital technology. This chapter will be devoted to op-amps and comparators, with a tailpiece on voltage references. This is not to deny the enormous range of other analogue functions that are available, but these are intended for specific niche applications and little can be generalised about them. Volumes have already been written about op-amp theory and circuit design and these aspects will not be repeated here. Rather, we shall take a look at the departures from the ideal op-amp parameters that are found in practical devices, and survey the tradeoffs - including cost and availability, as well as technical factors -that have to be made in real designs. Some instances of anomalous behaviour will also be examined. 5.1 The ideal op-amp The following set of characteristics (in no particular order, since they are all unattainable) defines the ideal voltage gain block: • infinite input impedance, no bias current • zero output impedance • arbitrarily large input and output voltage range • arbitrarily small supply current • infinite open-loop gain • zero input offset voltage and current • zero noise contribution • absolute insensitivity to temperature, power rail and common-mode input fluctuations • zero cost • off-the-shelf availability in any package • compatibility between different manufacturers • perfect reliability Since none of these features are achievable, you have to select a practical op-amp from the multitude of imperfect types on the market to suit a given application. Some basic examples of tradeoffs are • a high-frequency ac amplifier will need maximum gain bandwidth but won't be interested in bias current or offset voltage Chapter 5
- Dennis L. Eggleston(Author)
- 2011(Publication Date)
- Cambridge University Press(Publisher)
6 Operational amplifiers 6.1 Introduction We now turn to an examination of the properties and uses of the operational amplifier or op-amp . A detailed analysis of this multi-stage amplifier circuit is beyond the scope of this text, so we will treat it as a black box device as we did earlier with the voltage regulator. Thus, to use the device, we need only learn and apply some simple rules and, later, the real-world limitations of the device. In current usage, the operational amplifier is usually packaged as an integrated circuit with multiple leads or pins. While there are hundreds of different op-amps with different specifications, they all follow the same usage rules. To be specific, we will focus on a “classic” version: the 741 op-amp. The circuit symbol for the op-amp is shown in Fig. 6.1 . There are inputs for two power supply voltages (one positive and one negative relative to ground, labeled V + cc and V − cc , respectively). There are also two signal inputs: the inverting input , labeled with a minus sign, and the non-inverting input , labeled with a plus sign. Happily, there is only one output. As we know, voltages are always between two points, but our description of the op-amp inputs seems to refer to voltages at one point, the various input pins. It is thus important to note that all of the voltages for the op-amp are referenced to ground (i.e., the second point is ground). While it is common for writers discussing op-amp circuits to refer to the voltage at some point, one should keep in mind that they are really talking about the voltage between this point and ground. Also, the power supply connections shown in Fig. 6.1 are often omitted from circuit diagrams for simplicity, and it is easy for the novice building such a circuit to forget these connections. Of course, the circuit will not work without them. The basic operation of the op-amp can be simply stated.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- The English Press(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter- 4 Operational Amplifier A Signetics μa741 operational amplifier, one of the most successful op -amps. An Operational amplifier (op-amp) is a DC-coupled high-gain electronic voltage amplifier with a differential input and, usually, a single-ended output. An op-amp pro-duces an output voltage that is typically hundreds of thousands times larger than the voltage difference between its input terminals. Operational amplifiers are important building blocks for a wide range of electronic circuits. They had their origins in analog computers where they were used in many linear, non-linear and frequency-dependent circuits. Their popularity in circuit design largely stems from the fact the characteristics of the final elements (such as their gain) are set by ________________________ WORLD TECHNOLOGIES ________________________ external components with little dependence on temperature changes and manufacturing variations in the op-amp itself. Op-amps are among the most widely used electronic devices today, being used in a vast array of consumer, industrial, and scientific devices. Many standard IC op-amps cost only a few cents in moderate production volume; however some integrated or hybrid opera-tional amplifiers with special performance specifications may cost over $100 US in small quantities. Op-amps may be packaged as components, or used as elements of more complex integrated circuits. The op-amp is one type of differential amplifier. Other types of differential amplifier include the fully differential amplifier (similar to the op-amp, but with two outputs), the instrumentation amplifier (usually built from three op-amps), the isolation amplifier (similar to the instrumentation amplifier, but with tolerance to common-mode voltages that would destroy an ordinary op-amp), and negative feedback amplifier (usually built from one or more op-amps and a resistive feedback network).
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Research World(Publisher)
________________________ WORLD TECHNOLOGIES ________________________ Chapter 4 Operational Amplifier A Signetics μa741 operational amplifier, one of the most successful op -amps. An operational amplifier (op-amp) is a DC-coupled high-gain electronic voltage amplifier with a differential input and, usually, a single-ended output. An op-amp pro-duces an output voltage that is typically hundreds of thousands times larger than the voltage difference between its input terminals. ________________________ WORLD TECHNOLOGIES ________________________ Operational amplifiers are important building blocks for a wide range of electronic circuits. They had their origins in analog computers where they were used in many linear, non-linear and frequency-dependent circuits. Their popularity in circuit design largely stems from the fact that characteristics of the final elements (such as their gain) are set by external components with little dependence on temperature changes and manufacturing variations in the op-amp itself. Op-amps are among the most widely used electronic devices today, being used in a vast array of consumer, industrial, and scientific devices. Many standard IC op-amps cost only a few cents in moderate production volume; however some integrated or hybrid operational amplifiers with special performance specifications may cost over $100 US in small quantities. Op-amps may be packaged as components, or used as elements of more complex integrated circuits. The op-amp is one type of differential amplifier. Other types of differential amplifier include the fully differential amplifier (similar to the op-amp, but with two outputs), the instrumentation amplifier (usually built from three op-amps), the isolation amplifier (similar to the instrumentation amplifier, but with tolerance to common-mode voltages that would destroy an ordinary op-amp), and negative feedback amplifier (usually built from one or more op-amps and a resistive feedback network).
No longer available |Learn more- (Author)
- 2014(Publication Date)
- College Publishing House(Publisher)
____________________ WORLD TECHNOLOGIES ____________________ Chapter 10 Operational Amplifier A Signetics μa741 operational amplifier, one of the most successful op-amps An Operational amplifier (op-amp) is a DC-coupled high-gain electronic voltage amplifier with a differential input and, usually, a single-ended output. An op-amp produces an output voltage that is typically hundreds of thousands times larger than the voltage difference between its input terminals. Operational amplifiers are important building blocks for a wide range of electronic circuits. They had their origins in analog computers where they were used in many linear, non-linear and frequency-dependent circuits. Their popularity in circuit design largely stems from the fact the characteristics of the final elements (such as their gain) are set by external components with little dependence on temperature changes and manufacturing variations in the op-amp itself. ____________________ WORLD TECHNOLOGIES ____________________ Op-amps are among the most widely used electronic devices today, being used in a vast array of consumer, industrial, and scientific devices. Many standard IC op-amps cost only a few cents in moderate production volume; however some integrated or hybrid operational amplifiers with special performance specifications may cost over $100 US in small quantities. Op-amps may be packaged as components, or used as elements of more complex integrated circuits. The op-amp is one type of differential amplifier. Other types of differential amplifier include the fully differential amplifier (similar to the op-amp, but with two outputs), the instrumentation amplifier (usually built from three op-amps), the isolation amplifier (similar to the instrumentation amplifier, but with tolerance to common-mode voltages that would destroy an ordinary op-amp), and negative feedback amplifier (usually built from one or more op-amps and a resistive feedback network).
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Academic Studio(Publisher)
____________________ WORLD TECHNOLOGIES ____________________ Chapter- 10 Operational Amplifier A Signetics μa741 operational amplifier, one of the most successful op -amps. An operational amplifier (op-amp) is a DC-coupled high-gain electronic voltage amplifier with a differential input and, usually, a single-ended output. An op-amp produces an output voltage that is typically hundreds of thousands times larger than the voltage difference between its input terminals. Operational amplifiers are important building blocks for a wide range of electronic circuits. They had their origins in analog computers where they were used in many linear, non-linear and frequency-dependent circuits. Their popularity in circuit design largely stems from the fact the characteristics of the final elements (such as their gain) are set by external components with little dependence on temperature changes and manufacturing variations in the op-amp itself. ____________________ WORLD TECHNOLOGIES ____________________ Op-amps are among the most widely used electronic devices today, being used in a vast array of consumer, industrial, and scientific devices. Many standard IC op-amps cost only a few cents in moderate production volume; however some integrated or hybrid operational amplifiers with special performance specifications may cost over $100 US in small quantities. Op-amps may be packaged as components, or used as elements of more complex integrated circuits. The op-amp is one type of differential amplifier. Other types of differential amplifier include the fully differential amplifier (similar to the op-amp, but with two outputs), the instrumentation amplifier (usually built from three op-amps), the isolation amplifier (similar to the instrumentation amplifier, but with tolerance to common-mode voltages that would destroy an ordinary op-amp), and negative feedback amplifier (usually built from one or more op-amps and a resistive feedback network).
- J. David Irwin, David V. Kerns, Jr.(Authors)
- 2022(Publication Date)
- Wiley(Publisher)
CHAPTER 10 Operational Amplifiers and Applications LEARNING OBJECTIVES • To understand the characteristics of operational amplifiers and differential amplifiers • To understand the operation of the ideal op-amp model • To be able to recognize and analyze fundamental op-amp circuits • To understand the application of op-amps in the development of low-pass, high-pass, and bandpass filters • To be able to understand the use of op-amps to construct differentiator and integrator circuits • To understand multistage amplifier circuits • To be able to use op-amps in instrumentation and laboratory measurements and in industrial applications. INTRODUCTION The operational amplifier, or op amp as it is commonly known, is a fundamental component in analog electronic systems. Although it can be used in a variety of applications, it is widely used in instrumentation and measurement systems. An actual circuit diagram for a commercial op amp is the 741 Op Amp shown in Figure 10.1. Also shown in the figure are the pin connections for a dual in-line package, or DIP, which sup- ports its connection with other electronic components. Even a cursory examination of the circuit schematic for the op amp indicates that this is not a trivial network. It is typically constructed as an integrated circuit and may be purchased as a single device, in a DIP that contains several op amps or in a “surface mount” package. These elements are not only powerful devices in analog circuit design but are also inexpensive – less than a dollar for a chip in a package. Even after wading through the chapters in this book and developing a knowledge of transis- tors and their applications, the circuit diagram in Figure 10.1 may appear formidable. However, as sophisticated as it appears, it is really nothing more than a high-quality linear voltage ampli- fier. The details of how this circuit is designed are beyond the scope of this book, but follows basic principles described here.
eBook - PDF- J. David Irwin, R. Mark Nelms(Authors)
- 2021(Publication Date)
- Wiley(Publisher)
120 CHAPTER 4 4.1 Introduction It can be argued that the operational amplifier, or op-amp as it is commonly known, is the single most important integrated circuit for analog circuit design. It is a versatile intercon- nection of transistors and resistors that vastly expands our capabilities in circuit design, from engine control systems to cellular phones. Early op-amps were built of vacuum tubes, making them bulky and power hungry. The invention of the transistor at Bell Labs in 1947 allowed engineers to create op-amps that were much smaller and more efficient. Still, the op-amp itself consisted of individual transistors and resistors interconnected on a printed circuit board (PCB). When the manufacturing process for integrated circuits (ICs) was developed around 1970, engineers could finally put all of the op-amp transistors and resistors onto a single IC chip. Today, it is common to find as many as four high-quality op-amps on a single IC for as little as $0.40. A sample of commercial op-amps is shown in Fig. 4.1. (a) (b) FIGURE 4.1 A selection of op-amps. On the left (a) is a discrete op-amp assembled on a printed circuit board (PCB). On the right, top-down, a LM324 DIP, LMC6492 DIP, and MAX4240 in a SO-5 package (small outline/5 pins). The Apex Microtechnology PA03 with its lid removed (b) showing individual transistors and resistors. (Left, Courtesy of Mark Nelms and Jo Ann Loden; right, Courtesy of Apex Microtechnology Corp.) Operational Amplifiers LEARNING OBJECTIVES The learning goals for this chapter are that students should be able to: • Apply the model of the op-amp device to determine the currents and voltages in a circuit. • Analyze a variety of circuits that employ op-amps. • Use the model of the op-amp in a number of practical applications to determine the output voltage and/or current with respect to the input voltage(s) and current(s).
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