DIGITAL ELECTRONICS

THE TRANSISTOR AS AN AMPLIFIER AND AS A SWITCH THE BJT TRANSISTOR AS AN AMPLIFIER In electronics, the bipolar junction transistor (abbreviation commonly used: BJT , from the English bipolar junction transistor ) is a type of transistor widely used in the field of analog electronics mainly as a current amplifier and switch. It constitutes the most widespread family in electronics together with the field effect transistor with respect to which it is able to offer a greater output current with the disadvantage, however, of not having an isolated control terminal ( gate ). It is composed of [...]

THE LOGICAL FAMILIES In digital electronics, the logic family is a circuit-level embodiment of a digital logic component. In integrated circuits it represents a set of logic gates made by means of a particular design, characterized by the same logic levels and supply voltage. In the past, logic families were implemented as individual components, each of which containing one or more elementary logic functions, which formed the basis for the implementation of more complex logic blocks. Each logic family is characterized by a main logic function, which corresponds to the basic logic gate of the family, which is usually [...]

THE INTEGRATED CIRCUIT An integrated circuit ( IC , from the English integrated circuit ), in digital electronics, is a miniaturized electronic circuit where the various transistors have all been formed at the same time thanks to a single physical-chemical process. A chip (lit. "piece") is the electronic component made up of a tiny silicon wafer plate ( die ), from which the integrated circuit is built; in practice, the chip is the support that contains the elements (active or passive) that make up the circuit. Sometimes the term chip is used to indicate the integrated circuit as a [...]

THE LOGICAL GATES AND OR NOT A logic gate , in digital electronics and information technology, is a digital circuit capable of implementing (that is, of realizing, simulating its "mathematical logic" by means of suitable controls on electrical signals) a particular logical operation of one or more Boolean variables. This definition will be clearer when we talk about Boolean algebra. In this post we will introduce logic gates. Let's start with the fundamental logic gates (to then see all the others) capable of performing the operations of addition, product and negation indicated, respectively, with OR (logical sum), AND (logical [...]

BOOLE'S ALGEBRA Boolean algebra is an abstract algebra that operates with only the values ​​0 and 1 associated with the truth values ​​False and True (Boolean Logic). Algebra was developed in 1854 at University College Cork by Boole to write the logic of propositions in algebraic form. Today it forms the basis of the digital world. You study Boolean algebra or Boolean algebra because a digital circuit can be expressed through a boolean expression and vice versa (boolean logic). A Boolean function has one or more input variables and the output depends exclusively on the states assumed by the [...]

ADDING CIRCUITS Addition is the most basic of arithmetic operations. Adding binary numbers is pretty much like adding decimal numbers, to add two numbers like 245 and 673, you break the problem down into simpler steps. Each step only requires adding a couple of decimal digits. In this example we would start with 5 plus 3 (etc.). Binary adders are combinatorial networks which receive n bits of the addends to be added as input and generate the bits of the binary sum with the relative carry as output. It is, therefore, a typical example of a combinatorial network with [...]

MULTIPLEXER DEFINITION The Multiplexer, also called MUX , is a combinatorial digital circuit able to select one of 2n input lines (data lines) and to report the values ​​of this line on a single output. For this purpose, in general, the circuit has, in addition to the data inputs, also n selection inputs. The figure below shows the simple block diagram of a MUX with 2 data inputs and 1 selection input. AND' a data line selector able to select different input signals both analog and digital. Once selected, the signals are collected and sent to a single output [...]

DEMULTIPLEXER DEFINITION A demultiplexer (or demux) is a device that takes a single line of input and routes it to one of several digital output lines. A demux of 2 n outputs has n select lines, which are used to select which output line to send input to. A demux is also called a data distributor. Demuxes can be used to implement general purpose logic. By setting the input to true, the demux acts like a decoder. DEMULTIPLEXER OPERATION The operation is similar to the MUX, both as regards the selection and as regards the activation of the AND [...]

MULTIVIBRATORS Multivibrators are circuits suitable for supplying square, rectangular and impulsive waves. Made in various forms, with transistors, operational amplifiers, logic gates, integrated circuits, they are divided into astable, monostable and bistable: Astable Multivibrator: it is characterized by two states between which the multivibrator oscillates without the need for external commands. The astable is a real generator of square and rectangular waves. Monostable : also called one-shot, this multivibrator has a stable state, in which it can remain indefinitely, and a quasi-stable state. By means of an input command signal (trigger signal) it is possible to switch the monostable [...]

MONOSTABLE CIRCUIT A monostable multivibrator can be used as circuit delay. Such a circuit it can receive a very fast signal as input and produce a signal with a well-determined active time as output . Think of the lights on the stairs of an apartment building. After being triggered by a switch, the lights remain on for a period of time set by the timer. It is possible to create a monostable both in positive and negative logic, ie which responds with a logic level 0 or 1 at the output and activated by the same logic at the [...]