CASAModB1-04ElectronicFundamentalsB1-Intergrated circuts and op amps.pdf

Integrated Circuits and Operational Amplifiers (4.1.3.1) Learning Objectives 4.1.3 Describe the differences between a digital and an analogue systems (S). 4.1.3.1 Describe the basic layout and operation of logic circuits, linear circuits and operational amplifiers (Level 1). Su...

Integrated Circuits and Operational Amplifiers (4.1.3.1) Learning Objectives 4.1.3 Describe the differences between a digital and an analogue systems (S). 4.1.3.1 Describe the basic layout and operation of logic circuits, linear circuits and operational amplifiers (Level 1). Summary This lesson introduces integrated circuits. Integrated circuits can contain both linear circuits and logic circuits. This section will focus primarily on the linear integrated circuits and their applications. Logic integrated circuits will be introduced here, but a detailed explanation of logic circuits and their applications are explained in Module 05 - Digital Techniques. 2022-11-10 B1-04 Electronic Fundamentals Page 93 of 163 CASA Part 66 - Training Materials Only  Digital Systems Digital vs Analogue Systems A digital system is a combination of devices designed to manipulate logical information or physical quantities that are represented in digital form; that is, the quantities can take on only discrete values. These devices are most often electronic, but they can also be mechanical, magnetic or pneumatic. Some of the more familiar digital systems include digital computers and calculators, digital audio and video equipment and the telephone system—the world’s largest digital system. An analogue system contains devices that manipulate physical quantities that are represented in analogue form. In an analogue system, the quantities can vary over a continuous range of values. For example, the amplitude of the output signal to the speaker in a radio receiver can have any value between zero and its maximum limit and an infinite number of points in between. Other common analogue systems are audio amplifiers, magnetic tape recording and playback equipment and a simple light dimmer switch. ANALOGUE DIGITAL Aviation Australia Analogue vs digital data 2022-11-10 B1-04 Electronic Fundamentals Page 94 of 163 CASA Part 66 - Training Materials Only  Integrated Circuits and Logic Microelectronics Up to now the various semiconductors, resistors, capacitors, etc., in our discussions have been considered as separately packaged components, called discrete components. In this section we will introduce some of the more complex devices that contain complete circuits packaged as a single component. These devices are referred to as integrated circuits (ICs), and the broad term used to describe the use of these devices to miniaturise electronic equipment is microelectronics. Discrete circuit and equivalent integrated circuit size comparison (IC 555 Timer circuit) 2022-11-10 B1-04 Electronic Fundamentals Page 95 of 163 CASA Part 66 - Training Materials Only  The Introduction of Microelectronics This integrated circuit was produced in about 1960 by Fairchild Semiconductor. It is a bi-stable RS (Reset/Set) Flip-Flop constructed using four NPN bipolar transistors and two resistors diffused into a single chip of silicon. The maximum operating clock speed is 1 megahertz and the delay is 50 nanoseconds. An early IC from 1960 containing four NPN transistors and two resistors Integrated Circuits An integrated circuit is a device that integrates (combines) both active components (transistors, diodes, etc.) and passive components (resistors, capacitors, inductors, etc.) of a complete electronic circuit in a single chip (a tiny slice or wafer of semiconductor crystal or insulator). Integrated circuits (ICs) have almost eliminated the use of individual electronic components (resistors, capacitors, transistors, etc.) as the building blocks of electronic circuits. Instead, tiny chips have been developed whose functions are not that of a single part, but of dozens of transistors, resistors, capacitors and other electronic elements, all interconnected to perform the task of a complex circuit. Often these comprise a number of complete conventional circuit stages, such as a multistage amplifier, logic circuits, linear circuits and operational amplifiers (in one extremely small component). These chips are frequently mounted on a printed circuit board which plugs into an electronic unit. 2022-11-10 B1-04 Electronic Fundamentals Page 96 of 163 CASA Part 66 - Training Materials Only  Integrated circuits have several advantages over conventional wired circuits of discrete components. These advantages include: Drastic reduction in size and weight Large increase in reliability Lower costs Possible improvement in circuit performance. Lower power consumption Less heating load. However, integrated circuits are composed of parts so closely associated with one another that repair becomes impossible. In case of trouble, the entire circuit is replaced as a single component. Integrated circuits are being used in an ever increasing variety of aviation applications. Small size and weight and high reliability make them ideally suited for use in airborne equipment, missile systems, onboard computers, spacecraft and portable equipment. They are often easily recognised because of the number of connections to the integrated circuit. These tiny packages protect and help dissipate heat generated in the device. One of these packages may contain one or several stages, often having several hundred components. Aviation Australia Integrated circuits on a printed circuit board 2022-11-10 B1-04 Electronic Fundamentals Page 97 of 163 CASA Part 66 - Training Materials Only  Logic Integrated Circuits Nonlinear Circuits A digital logic circuit is a type of nonlinear circuit. It is a discrete (digital) circuit, meaning it doesn't deal with analogue type data (voltage levels), instead it deals with discrete representations of data (numbers representing value). For example, an analogue to digital converter (ADC) might convert an analogue voltage to a number (representing the physical value measured) and from there it might be processed through logic circuitry to produce the desired outcome. Logic Gates and Logic Circuits Logic circuits perform logic on a given discrete input using logic gates. Logic circuits exist to carry out a set of logic actions that can be used in any computer device from control used in washing machines, recorders, security systems, flight control systems and a host of industrial control actions. Simple arithmetic actions can also be carried out via logic circuits. All logic actions, however complicated, can be broken down into simple actions that are called AND, OR, and NOT, so that logic elements (special switching electric circuits) called gates, which carry out such actions, are the basis of all complex computing. Logic Integrated Circuits A logic integrated circuit is a singular electronic device which contains entire logic circuit(s) within. The term integrated circuit is broad and can mean anything from a simple device housing a small circuit to a complex device housing millions of logic circuits. Large ICs can house thousands to billions of transistors within and can perform very complex logic. The particularly complex types of integrated circuits are known as microprocessors and are used as the central processing units (CPUs) in computers. © Aviation Australia Logic ICs work with discrete values 2022-11-10 B1-04 Electronic Fundamentals Page 98 of 163 CASA Part 66 - Training Materials Only  Logic circuits are the basis of all modern computer technology and run the logic utilised by computer processors. The AND Function The AND function can be shown by the intersection of 2 or more circles representing physical conditions, in the diagram, there are 3 circles representing the the conditions required for fire. If one of the circle parameters is zero then there will be no fire. Aviation Australia AND Function Where fire occurs, all 3 inputs must be available. If any one parameter is missing there will be no fire. It could be thought of in electrical terms as 3 series switches where power is only output when all switches are closed (shown in the following diagram - LHS). There will be no power out is any switch is open. This fire scenario can also be translated into a truth table (shown in the following diagram - RHS). © Aviation Australia AND Function fire example 2022-11-10 B1-04 Electronic Fundamentals Page 99 of 163 CASA Part 66 - Training Materials Only  The OR Function © Aviation Australia OR Function - Master Fire Warning The OR function can be represented by the area of 2 or more circles representing physical conditions, in the diagram, the master fire warning can be illuminated by either engine or the test switch, i.e. anything within the area of the 3 circles. If any input is on, the lamp will be illuminated. Aviation Australia OR Function - Circuit representation and truth table Here the switches representing the circles are connected in parallel so any switch closed will power the light. 2022-11-10 B1-04 Electronic Fundamentals Page 100 of 163 CASA Part 66 - Training Materials Only  The Not Function © Aviation Australia NOT Function - Circuit representation and truth table The NOT gate output is opposite to the input as can be seen by the representative circuit, when the switch is closed the lamp will go out and when the switch is open the lamp will illuminate. 2022-11-10 B1-04 Electronic Fundamentals Page 101 of 163 CASA Part 66 - Training Materials Only  Linear Integrated Circuits Linear Circuits The linear circuit is an analogue type of circuit, as opposed to the digital type. An analogue function has continuous values within a specified range, whereas a digital function has discrete values or steps. Linear circuits can be broken down into several main categories: 1. Operational Amplifiers Integrators Differentiators Voltage followers Electronic filters. 2. Voltage regulators 3. Communication circuits 4. Interface circuits Comparators Sense amplifiers Line drivers and receivers Analogue-to-digital (A to D) and digital-to-analogue (D to A) converters. 2022-11-10 B1-04 Electronic Fundamentals Page 102 of 163 CASA Part 66 - Training Materials Only  Linear Integrated Circuits A linear integrated circuit is a singular electronic device which contains an entire linear circuit within. For the circuits listed above, there are specific ICs to perform that given circuit functionality. © Aviation Australia Linear ICs work with analogue values 2022-11-10 B1-04 Electronic Fundamentals Page 103 of 163 CASA Part 66 - Training Materials Only  Operational Amplifiers The Operational Amplifier The standard operational amplifier (op-amp) symbol is shown below. It has two input terminals - the inverting (-) input and the non-inverting (+) input and one output terminal. © Aviation Australia Operational amplifier circuit symbols As shown above, the typical op-amp operates with two DC supply voltages, one positive and the other negative, as shown on the left. Usually, these DC voltage terminals are left off the schematic symbol for simplicity but are understood to be there (shown on the right). 2022-11-10 B1-04 Electronic Fundamentals Page 104 of 163 CASA Part 66 - Training Materials Only  © Aviation Australia Op amp physical component (8-pin) A commonly used operational amplifier is the 741 op-amp IC which is an 8-pin integrated circuit and is shown below in the pinout diagram. For simple operation Pins 1 and 5 do not have to be connected. © Aviation Australia 741 Op-amp component and pin-layout 2022-11-10 B1-04 Electronic Fundamentals Page 105 of 163 CASA Part 66 - Training Materials Only  The Ideal Op-Amp To illustrate what an op-amp is, let us consider its ideal characteristics. A practical op-amp, of course, falls short of these ideal standards, but it is much easier to understand and analyse the device from an ideal point of view. © Aviation Australia Ideal op-amp First, the ideal op-amp has: Infinite voltage gain and infinite bandwidth An infinite input impedance (open) so that it does not load the driving source A zero output impedance. The input voltage, Vin, appears between the two input terminals, and the output voltage is as indicated by the internal voltage source symbol as depicted in the diagram above. 2022-11-10 B1-04 Electronic Fundamentals Page 106 of 163 CASA Part 66 - Training Materials Only  The Practical Op-Amp Although modern IC op-amps approach parameter values that can be treated as ideal in many cases, the ideal device can never be made. Any device has limitations, and the IC op-amp is no exception. Op-amps have both voltage and current limitations. Peak-to-peak output voltage, for example, is usually limited to slightly less than the two supply voltages. Output current is also limited by internal restrictions such as power dissipation and component ratings. Aviation Australia Practical op-amp Characteristics of a practical op-amp are: Very high voltage gain around 20 000 to 200 000. Very high input impedance of approximately 2MΩ. Very low output impedance 75Ω. Wide bandwidth 100 000Hz to 1000 000Hz. 2022-11-10 B1-04 Electronic Fundamentals Page 107 of 163 CASA Part 66 - Training Materials Only  Operational Amplifier Operation A typical op-amp is made up of three types of amplifier circuit: a differential amplifier, a voltage amplifier and a push-pull amplifier, as shown in the illustration below. A differential amplifier is the input stage for the op-amp. It has two inputs and provides amplification of the difference voltage between the two inputs. Aviation Australia Internal block diagram of an op-amp Op-Amp Operation Typically, the gain of a good op-amp may be from 50 000 to 200 000 (LM741 op-amp and other op amps can reach a gain of 350 000). This means that any small signal detected on the input is amplified by up to 200 000 times its original amplitude. Of course, the applied circuit voltage would probably not support this range of amplification, but the op-amp output would be driven until it was as close to the supply voltage as it could get, meaning maximum voltage would be applied to the output (saturation). An op-amp operating like this would be termed to be operating in open-loop, that is it has no feedback to limit. For example, if only 1 millivolt were applied to the input, 0.01 volts x 50 000 gain = 500 volts. If the circuit is limited to a maximum of 15 volts (applied voltage), it would output 15V for even the tiniest of inputs. 2022-11-10 B1-04 Electronic Fundamentals Page 108 of 163 CASA Part 66 - Training Materials Only  Op-Amp Comparator © Aviation Australia Open-loop - Comparator with two in-phase input signals Open-loop operation can be used, most commonly as a Comparator. With the negative input connected to the reference voltage (0V in the diagram) and the input to the positive input. The output will try to be the input voltage multiplied by 200 000 (0.05 x 200 000 = 10 000) but is limited by the applied power supply voltages. When the input is above the reference voltage, the output will be close to the maximum positive supply voltage. When the input is below the reference voltage, the output will be close to the maximum negative supply voltage. Aviation Australia Comparator 2022-11-10 B1-04 Electronic Fundamentals Page 109 of 163 CASA Part 66 - Training Materials Only  Op-Amp Negative Feedback If the output signal is to be the same shape as the input only larger the amplification must be controlled, to keep it within the capability of the circuit. This is achieved by providing feedback. The feedback method used in an op-amp is negative feedback. The simplest type is the inverting amplifier. Part of the output voltage is fed back to the negative input is referred to as negative feedback, of just feedback. If part of the input was fed into the positive input it would be called positive feedback or feed-forward. © Aviation Australia Inverting op-amp Keep in mind the ideal op-amp has an infinite input impedance meaning the op-amp will draw no current from the input, so the only current flows between input and output. As the positive input is connected to 0V if the input is 0V the output would be zero. If the input is positive 10mV the output will start to go negative, the resistors act as a voltage divider network where the voltage at the op-amp input is pulled back towards 0V stopping the output going more negative. The final output is proportional to the resistances and input voltage. Consider the op-amp input to be zero, so the input (10mV) dropped across R and the current flowing through both resistors, in the diagram the resistor from the output to the negative input is 2R (feedback resistor) therefore the voltage dropped would be twice the input voltage. Thus any appropriate multiplication (op amp gain) of the input can be set by changing the ratio of the resistors. 2022-11-10 B1-04 Electronic Fundamentals Page 110 of 163 CASA Part 66 - Training Materials Only  Op-Amp Voltage Follower Analogue applications use an Op-Amp that has some amount of negative feedback. The Voltage Follower Op-Amp will not amplify at all as it operates at Unity Gain with a gain of 1, as the feedback resistor is the same value as the input resistor the output will be the same value but inverted. The value of R will be kept large in order to limit the current and reduce wasted energy. © Aviation Australia Inverting voltage follower Unity Gain arrangements are also called Voltage Followers since they track the input voltage at the exact same level at output. Sometimes, you will want an output that is Inverting, and sometimes you want one that is Non-Inverting. © Aviation Australia Non-inverting voltage follower In the non-inverting voltage follower, the output voltage becomes the reference voltage in the comparator the input is basically adjusting the reference voltage so the output equals the input voltage and polarity, or it can be thought of as 100% negative feedback limiting the output voltage to the input voltage. 2022-11-10 B1-04 Electronic Fundamentals Page 111 of 163 CASA Part 66 - Training Materials Only