4.1.3 Integrated Circuits Flashcards
Integrated Circuits (IC) are a combination of several electronic components in a common housing. The major advantage is the very high density of the components.
(IC’s) integrated circuits
The small housing and, therefore, the small surface can be a disadvantage because some additional cooling such as a heatsink or fan may be required. Another disadvantage is that ICs cannot be repaired, and a defective IC must always be replaced.
the following components are integrated into ICs
Semiconductors (transistors, diodes)
Resistors
Capacitors
Inductances cannot usually be integrated due to their large space requirements.
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Logic Circuits
Logic circuits are created on ICs and are made up of individual logic gates, that when assembled, perform the desired function
This type of circuit is designed to accept and generate voltage signals corresponding to binary 1s and 0s
Transistors are used to construct these circuits that act as digital logic gates.
The TRUE (1 state) output of the logic device is to have the lamp lit. If the lamp is not lit, then the output of the logic device is FALSE (0 state).
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three basic gates will be considered:
AND
OR
NOT
The NOT gate, also known as an inverter, is the simplest of all gate
If the input to the gate is logic 1, then the output is NOT logic 1, which means that it is logic 0. vice versa
An AND gate only has an output of 1 if all the inputs are 1.
The Boolean algebra for an AND gate is X = A.B (the . signifies AND)
The OR gate differs from the AND gate in that only one input must be HIGH to produce a HIGH output. An easy way to remember the OR gate is that any HIGH input will yield a HIGH output. This is the equivalent of two switches in parallel with each other.
The Boolean algebra for an OR gate is X = A+B (the + signifies OR).
OR gate
a logic 0 at A and B produces a 0 at X therefore the light remains OFF. Logic 1 at A and/or B means both the transistors will switch on and the light switches on.
The NAND gate is a combination of an AND gate and a NOT gate.
This means that AND gate conditions must be met and then inverted. So, the NAND gate is an AND gate followed by a NOT gate.
A NOR gate is similarly arranged to a NAND except that it is an inverted OR gate. If there is to be a logic 1 output, then neither input can be logic 1. This is the same as satisfying the OR gate conditions and then putting the output through a NOT gate.
The exclusive OR gate is a modified OR gate that produces a HIGH (logic 1) output when only one of the inputs is HIGH (logic 1). The abbreviation XOR is often used to identify this gate. When both inputs are at logic 1 or when both inputs are at logic 0, the output is 0.
XOR. F = A⊕B is the Boolean algebra
Integrated circuits that operate over an entire range of continuous values of the signal amplitude are called analogue integrated circuits.
Analogue Integrated Circuits are further classified into the two types they are:
- Linear Integrated Circuits
- Radio Frequency Integrated Circuits
Linear Integrated Circuits − An analogue IC is said to be linear if there exists a linear relationship between its voltage and current.
IC 741, an eight pin Dual In-line Package (DIP or DIL) Op-Amp, is an example of linear IC
Radio Frequency Integrated Circuits − An analogue IC is said to be non-linear if there exists a non-linear relation between its voltage and current.
A non-linear IC is also called a radio frequency IC.
A linear circuit is one in which the output is directly proportional to the input
If graphed, the performance of the circuit is drawn as a straight line. The straight line is the ideal linear output, but if the gain is too high the linear relationship between the current and the voltage is lost, and the output signal is clipped.
A linear component is one in which a linear relationship exists between the input current and the output voltage
Linear circuits are easy to analyse mathematically. The sum of the inputs to a linear circuit is equal to the output.
The most used linear integrated circuit is an operational amplifier, commonly known as an Op-Amp
It is a high-gain differential amplifier where the output is proportional to the difference between the two input signals
An Op-Amp has two inputs, an inverting input (-) and a non-inverting input (+), and one output
he polarity of the signal applied to the inverting input will be reversed at the output. A signal applied to the non-inverting input will keep its polarity at the output
To be classified as an operational amplifier, the device must have a very high gain, very high input impedance, and very low output impedance.
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Op-Amps are used in a wide variety of electronic circuits, including signal processing circuits, control circuits, and instrumentation.
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An Operational Amplifier (Op-Amp) is an integrated circuit that can amplify weak electric signals and has two input pins and one output pin. Its basic role is to amplify and output the voltage difference between the two input pins.
Unlike a transformer that can only amplify voltage or current, the Op-Amp also amplifies power output.
An operational amplifier is not used alone but is designed to be connected to other circuits to perform a great variety of operations.
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Symbols and Terminals
The standard Op-Amp symbol has two input terminals, the inverting input ( - ) and the non-inverting input ( + ) and one output terminal.
The typical operational amplifier requires two DC supply voltages, one positive and the other negative,
Usually, these DC voltage terminals are left off the schematic symbol for simplicity, but they are always understood to be there.
from the top of the IC the pins are numbered in an anti-clockwise direction. It is common practice to identify pin number 1 with a marker, which is usually a dot.
.Whenever a notch is seen in a chip outline, turn the board so that the notch is at the left. In that orientation, pin 1 is the bottom left pin, just below the notch.
An Op-Amp is an amplifier designed to be used with other circuit components to perform either computing functions such as addition and subtraction, or some type of transfer operation, such as filtering.
Operational amplifiers are usually high-gain amplifiers with the amount of gain determined by feedback.
Op-Amps have been in use for some time and were originally developed for analogue, non-digital, computers and used to perform mathematical functions.
They were not used in many other devices as they were expensive and more complicated than other circuits.
Today many devices use operational amplifiers and typical uses are
DC amplifiers
AC amplifiers
Comparators
Oscillators
Filter circuits
Many other applications
Operational amplifiers consist of several amplifier stages. The input stage is always a differential amplifier, and the output stage is usually a push-pull power amplifier.
As operational amplifiers are manufactured using integrated technology
Operational amplifiers are usually supplied with both a positive and a negative operating voltage.
The IC in which an Op-Amp is installed requires a minimum of 7 pins so Op-Amps normally 8 pin DIP/DIL construction
These are not polarity signs,
the – indicates the inverting input terminal and the + the non-inverting input terminal
the ‘-’ sign indicates 180° phase shift. the ‘-’ input is referred to as the ‘inverting input
‘+’ sign indicates zero phase shift
Most (but not all) operational amplifiers require a symmetrical supply of typically between ±5 V and ±15V
This allows the output voltage produced by the amplifier to swing both positive (above 0 V) and negative (below 0 V).
The output voltage is measured between the output terminal (pin 6) and the common terminal (pin 4) for both operating voltages.
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the common connection to these two supplies acts as the common 0 V rail and the input and output voltages are usually measured relative to this rail. So, if the voltage was +/- 30 V DC then the voltage output can swing 15 V on side of the 0 V rail
If the amplifier is not configured correctly e.g., greater than the +/-15 V DC, the output signal will be clipped or saturated
Like most engineered systems, the Op-Amp uses feedback to realise its potential value. Feedback comes in two forms:
- Connecting the output to the non-inverting input gives positive feedback.
- Connecting the output to the inverting input gives negative feedback.
b is the symbol used for feedback.
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Positive Feedback
In electronics, feedback is the return part of the output signal. If the output signal is fed back in phase, the input increases and so the output increases. This is regenerative or positive feedback.
Positive feedback increases gain: but if the feedback energy is sufficient to overcome the power lost by the resistances, the amplifier becomes unstable and produces oscillations and distortion.
Negative Feedback
When the feedback is out of phase with the input, the gain of the amplifier decreases, but the stability and bandwidth increase and there is a decrease in distortion. This is negative feedback.
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Gain
The key idea is that amplifiers give us power gain. There are two key points:
Amplify signals, which are time-varying quantities.
Amplified signals have more power.
The three gains are voltage, current, and power
Op-Amps are defined by their usage with the most common ones being
Inverters
Buffers (Voltage Follower)
Differential
Summing
Comparator
Inverters
The inverting operational amplifier is a constant or fixed-gain amplifier producing a negative output voltage as its gain is always negative.
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Buffers (Voltage Follower)
A buffer is a voltage follower unity gain, a non-inverting buffer that requires only an operational amplifier.
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Differential
The differential amplifier is a voltage subtractor circuit that produces an output voltage proportional to the voltage difference of two input signals.
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Summing
The summing amplifier is another type of operational amplifier circuit configuration that is used to combine the voltages present on two or more inputs into a single output voltage.
The difference between the summing Op-Amp and the differential type. The summing inputs are all on the inverting input and then compared to the non-inverting input which would be at ground potential i.e., zero.
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The comparator is an electronic decision-making circuit that makes use of an operational amplifier with a very high gain in its open-loop state. That is, there is no feedback resistor.
the Op-Amp comparator compares one analogue voltage level with another analogue voltage level or some preset reference voltage, Vref, and produces an output signal based on this voltage comparison
When an Op-Amp is configured as an integrator, the duration of the input signal is also considered. Therefore, an Op-Amp based integrator can perform mathematical integration concerning time.
The integrator produces an output voltage across the Op-Amp, which is directly proportional to the integral of the input voltage; therefore, the output is dependent on the input voltage over a period of time. The main difference is that the feedback resistor is replaced with a capacitor creating an RC network.
