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 Welcome to my web page dedicated to active electronic components.

I will try on this page to define with words suitable for everyone the immense world that lies behind the simple phrase "active electronic components", it is not an easy task but I will try. Of course, as already said on the other pages, it is impossible to condense a vast subject in this small text, but if you intend to delve deeper or need professional advice you can get in touch with me through the Contact page.

At the end of this document you will find links to in-depth pages dedicated to electronic and passive electronic components.

 

                      

                      Active electronic components

While passive components have only evolved in size and quality, active components, on the contrary, have experienced real earthquakes in their evolution over time, with entire systems and production concepts disappearing, replaced by other revolutionary systems and production concepts. We moved from thermoionic (or vacuum tube) components to solid-state systems around 1960, which started the revolution that allowed us to create everything we see now (smartphones, liquid crystal TVs, personal computers, tablets).
 Let's now get to know the main active components, they are transformers, thermionic tubes (also called valves), transistors and integrated circuits.

 

Transformers are defined as "active machines without moving parts" they are formed by two coils of copper wires mounted on a pack of laminations and separated by a core (see images at the end of the discussion) the coils are called one "primary" and the other "secondary" depending on the direction of operation. Transformers allow through the law of electromagnetic induction (Faraday-Neumann-Lenz law) to transfer by lowering or raising the value (transformation ratio), voltages and electric currents, they also ensure physical separation between circuits, since there is no contact between the primary and secondary, and they also act as impedance adapters in professional audio equipment. The size of a transformer depends on the current and voltage it must manage, the working voltage and current values ​​are usually printed directly on the transformer itself.

                    

               Low voltage transformers with various secondaries

 

                                                                                  

                                                             Electrical symbol of transformer

 

                                                         

                                           Three-phase high voltage pole transformer

 

 

                        

                                              Operating principle of tranformer

 

 

 

Thermionic tubes or electronic valves were the first active components that allowed the amplification and processing of electronic signals; they were used to make TVs, radios, transmitters and even computers (of gigantic dimensions).
They exploit the thermionic effect, which consists in the emission of electrons into the vacuum, by an electrode called "cathode", negatively polarized, made with a particular material, which is heated by an incandescent tungsten filament.

The emitted electrons moving in the vacuum do not have any particular obstacle and are attracted and collected by another positively polarized electrode called anode or plate, this is the thermionic diode, a component (also available in solid state) that allows current to pass through it in only one direction (direct polarization) and not in the other (reverse polarization).
If we add a third electrode called "grid" between the anode and the cathode, and we polarize it slightly negatively, we will be able to control and modulate the flow of electrons moving in the vacuum, in short by applying a small signal to the grid we will obtain a much larger signal on the anode, we have thus created a triode, the simplest thermoionic device, and also the first one created capable of amplifying an electrical signal, the electrodes are enclosed in a glass ampoule in which the vacuum has been obtained. If you need further information you can go to the contact section.

Multigrid tubes have been manufactured to meet special needs, tetrodes (two grids), pentodes (three grids) and tubes with a rarefied gas in the bulb rather than a vacuum. Although replaced in almost all applications by solid-state devices, they continue to be irreplaceable in some devices, such as high-frequency amplifiers of very high power and in high-end hi-fi applications for the particular mellow and pure sound that they are able to produce, even in the microwave oven that we all have at home there is a high-power tube to produce the very short-period emissions that cook food. And the cathode ray tube that until a few years ago allowed us to see splendid images on CRT TVs was a tube with the screen acting as the anode.

 

                     

                                    Thermionic tubes for radio and hi-fi applications

 

                                                                                        

                                                         Electrical symbol of vacuum triode

 

 

                                                                                           

                                                         Working principle of triode

 


        Semiconductor or solid-state devices.

They are particular active electronic components built by "doping" (introducing impurities) a semiconductor material (germanium, silicon or artificial semiconductors) in an appropriate manner.

The semiconductors are doped with positively charged P-type impurities (hole or lack of electron) or negatively charged N-type impurities (excess electrons). The contact between a P-charged semiconductor and another N-charged semiconductor produces a P-N junction. In the contact area, a current called depletion is created due to the exchange of charges in an attempt to restore the neutrality of the materials, thus creating a neutral area near the contact and a small insulating layer at the contact itself.

 It should be noted that the P-N junction, when exposed to direct sunlight, is able to produce an electrical voltage of 0.6V in the contact area. It therefore becomes a photovoltaic effect solar cell. By arranging many junctions (series and parallel) in an appropriate way, the photovoltaic panels currently used in production plants are obtained. If you need more information you can go to the contact page.

Using the properties of the P-N junction, it is possible to obtain all the components that are the basis of modern electronics, including solid-state diodes, TRANSISTORS, MOSFETs, JFETs, UJTs. These components can be made either in discrete form, that is, as a single component with certain characteristics, or as an integrated circuit, that is, a semiconductor crystal that, when appropriately doped, allows for the obtaining of a complete circuit of passive and active components in a very small space and with great savings in material and time. But let's take a closer look at the various types of semiconductor components.

 

                                   

                                                          P-N junction graphic illustration

 

                                                 

                                              Photovoltaic cell obtained from P-N junctions

 

 

The semiconductor diode uses a single P-N junction, which due to its known properties, is able to allow current to pass through it or not depending on how we apply voltage to it.

It has two external connections, one leads to the P-doped semiconductor (anode), the other to the N-doped semiconductor (cathode), if we apply voltage with the positive pole to the anode and the negative pole to the cathode, the diode will allow current to pass through it (forward polarization), if instead we invert the poles, the current will not be able to pass through the diode (reverse polarization).

Diodes can be used as rectifiers in power supplies, as switches, as detectors and as protection (in combination with a fuse) against reverse polarity of the power supply.
It should be noted that diodes have a threshold voltage of 0.6V for silicon diodes and 0.2V for germanium diodes, that is, if the voltage across their terminals in forward bias does not exceed this value, they behave like an open switch (no current flows), however silicon diodes with a lower threshold are manufactured (Schottky diode). There are also diodes that are used as variable capacitors (varicap diode) by varying the voltage across their terminals and particular voltage stabilizing diodes called Zener diodes.
 It is impossible not to mention the L.E.D. (light emitter diode), particular diodes that emit light from the P-N junction, then amplified by a special lens, they are revolutionizing the lighting sector thanks to the very low power consumption and the particular light that they are able to produce, from simple indicators they have evolved with the increase of the light emitted and with the obtaining of white light, lamps of all types and colors are currently manufactured, and they also provide the backlighting for the LCD screens (edge ​​LED) of the latest generation TVs.

 

 

                    

                                    Real diode, the white band is the cathode

 

                                 

                                                 Diode symbol used in electrical diagrams

 

                                                    

                                                                       LEDs of various colors

 

 

                                                                                       

                                            Internal diagram and symbol of LED diode

 

If you need further information or professional advice, you can go to the contact page.

 

 

The bipolar transistor or BJT is a component formed by two P-N junctions (see figure below), it can be of the PNP or NPN type, and has three terminals called, Base, Collector, Emitter (indicated in the electrical symbol by an arrow). It was discovered in 1946 in the Bell Telephone laboratories by researchers Walter Brattain, John Bardeen and William Schockley, they gave rise to modern electronics.

The transistor is an active current-controlled component capable of amplifying the signals applied to it, like the thermionic triode, but with many advantages, the main ones being that it is solid state and therefore difficult to destroy mechanically, it is small in size compared to tubes, it works with low voltages at the ends and its integration is relatively easy, furthermore it does not require filament voltage.

Very schematically, its operation can be defined as follows, "the electrons emitted by the emitter are regulated by the base and then collected by the collector".
They are used as amplifiers, switches, oscillators, regulators (combined with a Zener diode) and many other applications.

Transistors can be of the NPN or PNP type, this is decided during the production phase by doping the material constituting the three zones of the transistor with P-type or N-type impurities.

As solid-state component technology progressed, other transistors optimized for certain applications were introduced, including the JFET (junction field effect transistor) with high input impedance and voltage-controlled, the MOS-FET (switch with low channel resistance when forward biased) also voltage-controlled, and the UJT or unijunction (pulse oscillator).

Transistors are enclosed in metal or plastic containers depending on the required power dissipation and the possible application of a heat sink.

 

                                           

                                                       NPN transistor internal circuit diagram

 

 

                                                               

                                                                          BJT NPN symbol

 

 

                                                                                          

                                                         Power Transistor in TO220 Package

 

 

                                                   

                                                                      Transistor in TO92 package

 

 

                                                                         

                                                               Transistor in TO18 package

 

 

                                               

                                              Metal Power Transistor in TO3 Package

 

 

 

Finally, monolithic integrated circuits are made by doping the areas of a semiconductor chip in an appropriate way, in detail, by introducing more or less conductive impurities, insulators or conductors (or resistors of the desired value) will be created, P or N type impurities will create transistors with the desired characteristics, by doing so, a complex circuit will be obtained on a small semiconductor chip, accessible from the outside with terminals so as to be able to connect the passive components necessary for operation but not integrable (inductors, capacitors, resistors and others) to the outside.

There are analog and digital integrated circuits that perform very complex functions, it is thanks to them that it has been possible to miniaturize electronic circuits, with results visible to all, just think of tablets or smartphones, true miracles of electronic technology.

Integrated circuits are also produced that are built with normal components, without a container, then enclosed in plastic containers and performing simple functions, these types of components are called "hybrid integrated circuits". A very common example are the hybrid audio amplifiers or voltage regulators of the STK series.

 


 To know the characteristics of the active components, you must necessarily have the relevant datasheets.
Datasheets are information sheets, released by the manufacturer where you can find all the information regarding the maximum and minimum operating parameters of the components, and even examples of realizations, an excellent site where you can find datasheets of almost all active components can be found at this link.
Instead, by clicking on this link with the mouse you can view, as an example, the datasheet of a well-known component that has been in the spotlight for many years, the well-known TDA2003 low-frequency amplifier, capable of producing around ten Watts, using just a few external components. In the datasheet you will also find the internal diagram of the component, and examples of construction.

 

                                                 

                                                             Classic audio hybrid integrated circuit

                                       

                              Digital Integrated circuit in D.I.P. case

 

                      

                                        SMD dual in line integrated circuit (DIL)

 

                      

                                   Integrated circuit -5V negative voltage regulator

 

                      

                               SMD flatpack digital integrated circuit

 

 

Of course it is impossible to condense all these concepts in a small space, mine is only intended to be a good guide for those who are new to this fantastic world, it is however possible to delve deeper or request professional advice by contacting me, for this go to the contact page.


Thank you for visiting my website and following my guide, come back to visit it.

 

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