Early electronic components
Vacuum tubes were one of the earliest electronic components. They dominated electronics until the middle of the
1980s. Since that time, solid state devices have all but completely taken over. Vacuum tubes are still used in some
specialist applications such as high power RF amplifiers, cathode ray tubes, specialist audio equipment and some
microwave devices.
Types of circuits
Circuits and components can be divided into two groups: analog and digital. A particular device may consist of
circuitry that has one or the other or a mix of the two types.
Analog circuits
Hitachi J100 adjustable frequency drive chassis.
Most analog electronic appliances, such as radio receivers, are
constructed from combinations of a few types of basic circuits. Analog
circuits use a continuous range of voltage as opposed to discrete levels
as in digital circuits.
The number of different analog circuits so far devised is huge,
especially because a 'circuit' can be defined as anything from a single
component, to systems containing thousands of components.
Analog circuits are sometimes called linear circuits although many
non-linear effects are used in analog circuits such as mixers,
modulators, etc. Good examples of analog circuits include vacuum
tube and transistor amplifiers, operational amplifiers and oscillators.
One rarely finds modern circuits that are entirely analog. These days
analog circuitry may use digital or even microprocessor techniques to
improve performance. This type of circuit is usually called "mixed
signal" rather than analog or digital.
Sometimes it may be difficult to differentiate between analog and digital circuits as they have elements of both linear
and non-linear operation. An example is the comparator which takes in a continuous range of voltage but only
outputs one of two levels as in a digital circuit. Similarly, an overdriven transistor amplifier can take on the
characteristics of a controlled switch having essentially two levels of output.
Digital circuits
Digital circuits are electric circuits based on a number of discrete voltage levels. Digital circuits are the most
common physical representation of Boolean algebra, and are the basis of all digital computers. To most engineers,
the terms "digital circuit", "digital system" and "logic" are interchangeable in the context of digital circuits. Most
digital circuits use a binary system with two voltage levels labeled "0" and "1". Often logic "0" will be a lower
voltage and referred to as "Low" while logic "1" is referred to as "High". However, some systems use the reverse
definition ("0" is "High") or are current based. Ternary (with three states) logic has been studied, and some prototype
computers made. Computers, electronic clocks, and programmable logic controllers (used to control industrial
processes) are constructed of digital circuits. Digital signal processors are another example.
Building blocks:
• Logic gates
• Adders
• Flip-Flops
Electronics 3
• Counters
• Registers
• Multiplexers
• Schmitt triggers
Highly integrated devices:
• Microprocessors
• Microcontrollers
• Application-specific integrated circuit (ASIC)
• Digital signal processor (DSP)
• Field-programmable gate array (FPGA)