8. Introduction to
Electronic circuits
8.1.
Thermionic devices
8.2.
Semiconductor devices
8.3.
Distinction between Analogue and Digital electronics
8.4.
Comparison of digital electronics and analogue electronics.
8.5.
Analogue and Digital Systems
8.6.
Application examples
Introduction
Electrical Vs Electronic Circuits
Introduction
Electrical Vs Electronic Circuits
• Electrical devices are used to transform current into another form of energy e.g. motion, heat or light
• Electronic devices do also transform electrical energy to other forms but in addition they manipulate the current to fulfil a specific
task by adding meaningful data to current that flows through them thus enabling control of electrical circuits and information
provision.
• A device usually contains both electrical and electronic components for optimum operation.
• Electric circuits are used in the generation, transmission, and consumption of electric power and energy. (Electrical)
• Electric circuits are used in the encoding, decoding, storage, retrieval, transmission, and processing of information. (Electronic)
• Historically electronic devices consisted of vacuum tubes, however, with intensive research in semiconductor materials electronic
circuits consist of diodes, transistors, amplifiers, multiplexers and integrated circuits (ICs)
• Reading Assignment: Differentiate between Thermionic and Semiconductor Devices.
Electronic Circuits
Electronic Circuits
• In most electronic circuits, there are two inputs. One input is from a power supply that provides dc voltages and currents power the
electronic devices.
• The second input is a signal. Time-varying signals from a particular source very often need to be amplified before the signal is
capable of being “useful.
• The analysis of electronic circuits, then, is divided into two parts: one deals with the dc/ac input and its circuit response, and the
other deals with the signal input and the resulting circuit response.
• The signals that electronic devices are designed to process can be classified into two broad categories: analog and digital.
Electronic Circuits
• Analog signals can take on a continuous range of values, and thus represent continuously varying quantities; purely digital signals
can appear at only one of several discrete levels.
•
Much of the physical world is really analog in nature. Analog signals directly represent variables such as temperature, humidity,
pressure, light intensity, or sound—all of which may take on any value, typically within some finite range.
• When we speak of digital electronics, we are most often referring to electronic processing of binary digital signals, or signals that
can take on only one of two discrete amplitude levels as illustrated
•
The status of binary systems can be represented by two symbols: a logical 1 is assigned to represent one level, and a logical 0 is
assigned to the second level.2 The two logic states generally correspond to two separate voltages—VH and VL—representing the
high and low amplitude levels
The time-varying voltage or current plotted
in could be the electrical representation of
temperature, flowrate, or pressure versus
time, or the continuous audio output from a
microphone.
Electronic 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.
• 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 analog system contains devices that manipulate physical quantities that are represented in analog form. In an analog 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. Other common analog systems are audio amplifiers, a simple light dimmer switch.
• In many electronic systems, signals are processed, transmitted, and received in digital form. Digital systems and signal processing
are now a large part of electronics because of the tremendous advances made in the design and fabrication of digital circuits.
• Digital processing allows a wide variety of functions to be performed that would be impractical using analog means. In many cases,
digital signals must be converted from and to analog signals.
• These signals need to be processed through analog-to-digital (A/D) converters and digital-to-analog (D/A) converters.
D/A and A/D Systems
• For analog and digital systems to be able to operate together, we must be able to convert signals from analog to digital form and
viceversa.
• For analog to digital conversion, we sample the input signal at various points in time as illustrated and convert or quantize its
amplitude into a digital representation. The quantized value can be represented in binary form or can be a decimal representation
as given by the display on a digital multimeter.
• The electronic circuits that perform these translations are called digital-to-analog (D/A) and analog-to-digital (A/D) converters.
D/A and A/D Systems
Analog-to-Digital Conversion
• The analog-to-digital converter (A/D converter or ADC) is used to transform analog information in electrical form into digital data.
The ADC shown takes an unknown continuous analog input signal, usually a voltage vX, and converts it into an n-bit binary
number that can be easily manipulated by a computer. The n-bit number is a binary fraction representing the ratio between
the unknown input voltage vX and the converter’s full-scale voltage VFS.
Digital-to-Analog Conversion
• The digital-to-analog converter, often referred to as a D/A converter or DAC, provides an interface between the digital signals of
computer systems and the continuous signals of the analog world. The D/A converter takes digital information, most often in
binary form, as input and generates an output voltage vO or current that may be used for electronic control or analog information
display.
D/A and A/D Systems