Welcome to my web page dedicated to active electronic components


 
On this page I will try to define with words suitable for everyone the immense world behind the simple phrase
"electronic active components" is not an easy task but I will try. Of course, as already mentioned on the other pages, it is impossible to condense a vast subject in this small text, but if you intend to investigate further or you need professional advice, you can contact me via the Contacts page.

                         Active electronics components
                        
While the passive components had only dimensional and qualitative evolution, on the contrary the active components have known over time real earthquakes in their evolution, with entire systems and production concepts disappeared, replaced by other revolutionary systems and production concepts, we moved from thermionic (or vacuum) components to solid-state systems around 1960, which started the revolution that allowed us to achieve everything we see now (smartphones, LCD TVs, personal computers, tablets).
Now let's get to know the main active components, they are transformers, thermoionic tubes (also called valves), transistors and integrated circuits.

The electrical 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 a "primary" el 'other "secondary" depending on the direction of operation. Transformers allow through the law of electromagnetic induction (Faraday-Neumann-Lenz law) of transferring lowering or raising the value (transformation ratio), tensions and electric currents, they also ensure the physical separation between circuits, since there is no contact between the primary and secondary, and act also from impedance adapters in professional audio equipment. The size of a transformer depends on the current and the voltage it must manage, the working voltage and current values ​​are usually printed directly on the transformer itself.

    
                Low tension transformer                                Electrical symbol of the transformer

                                                                                                                                          
          

    Pole high voltage three-phase transformer                    Operating principle

Thermoionic tubes or electronic valves were the first active components to allow the amplification and processing of electronic signals, TVs, radios, transmitters, and even computers (of gigantic size) were made with them.
They exploit the thermoionic effect, which consists in the emission of electrons in the vacuum, by an electrode called "cathode", with negative polarity, made with a particular material, which is heated by an incandescent tungsten filament, the electrons emitted moving in a vacuum, they have no particular obstacle and are attracted and collected by another polarized electrode, positively called an anode or plate, this is the thermionic diode, a component (also available in solid state) that gets crossed by the current in a single sense (direct polarization) and not in the other (reverse polarization).
If we now add a third electrode called grid between anode and cathode, and polarize it slightly negative, we will be able to control and modulate the flow of electrons moving in a vacuum, in other words by applying a small signal to the grid we will get a signal much wider on the anode, we have thus realized a triode, the simplest thermoionic device, and also the first one realized able to amplify an electric signal, the electrodes are enclosed in a glass ampoule in which the vacuum has been obtained. If you need more information, you can go to the contact page.
Multi-grid tubes have been manufactured to satisfy particular needs, tetrodes (two grids), pentodes (three grids) and tubes having in the ampoule not the vacuum but a rarefied gas.
Although replaced in almost all applications by solid-state devices, they continue to be irreplaceable in some devices, such as in high-power high-frequency amplifiers, hi-fi applications for the particular and pure sound that they can produce, even in the oven There is a high-power valve in the microwave that we all have at home to produce the very short-term emissions that cook food. And the cathode ray tube that until a few years ago allowed us to see some splendid images on CRT TV was a valve with the screen acting as an anode.

                   
    Thermoionic tubes for radio applications         Electrical symbol of the vacuum triode 
                                          
                                       
                                                         Working principle of the triode

                     
                    Semiconductor or solid state devices

Particular active electronic components are constructed by doping (by introducing impurities) suitably a semiconductor material (germanium, silicon or artificial semiconductors), the semiconductors are doped with P-type impurities with positive charge (gap or lack of electron) or N-type with negative charge (excess of electrons), the contact between a charge P semiconductor with another with charge N produces a P-N type junction, in the contact zone a current called depletion is created due to the exchange of charges in the attempt to restore the neutrality of the materials, thus creating a neutral zone near the contact and a small insulating layer to the contact itself. It should be noted that the P-N junction subjected to direct sunlight is able to produce an electrical voltage of 0.6V (photovoltaic effect) in the contact zone, therefore it becomes a photovoltaic-effect solar cell, appropriately arranging many junctions (series and parallel) yes they get the photovoltaic panels currently used in production plants. If you need more information, you can go to the contact page.

Using the properties of the PN junction it is possible to obtain all the components that are the basis of modern electronics, including solid-state diodes, TRANSISTOR, MOSFET, JFET, UJT, these components can be made either in discrete form, ie as a single component with certain characteristics, or as an integrated circuit, or a semiconductor crystal that duly appropriately, allows to obtain a complete circuit of passive and active components in very little space and with great material and time savings, but let's get to know more from near the various types of semiconductor components.


               

   Graphic illustration of the P-N junction            Photovoltaic cell multiple P-N junction

The semiconductor diode uses a single P-N junction, due to its known properties, it is able to be crossed by current or not depending on how we apply voltage to it. It has two external connections, one being connected to the doped P
semiconductor (anode),
the other to that N (cathode), if we apply the voltage with the positive pole to the anode and the negative one to the cathode the diode will be crossed by the current (direct polarization), if instead we invert the poles the current will not be able to cross the diode (reverse polarization), they are used as rectifiers in power supplies, as switches, as detectors and as protection (combined with a fuse) against power supply polarity reversals.
Keep in mind that the diodes have a threshold voltage of 0.6V for those with silicon and 0.2V for those with germanium, ie if the voltage across them does not exceed this value they behave like an open switch (no current flows ), silicon diodes with lower threshold (Schottky diode), diodes are used which are used as variable capacitors (varicap diode) by varying the voltage at their ends and particular voltage stabilizing diodes called Zener diodes.
It is impossible then not to mention the L.E.D. (light emitter diode), special diodes that emit light from the PN junction, then amplified by a special lens, they are revolutionizing the field of lighting thanks to the very low current consumption and the particular light that they can produce, from simple indicators they they have evolved with the increase of the light emitted and with the obtainment of white light, lamps of all types and colors are currently manufactured, and also provide the backlight for the LCD screens (edge ​​LEDs) of the latest generation TVs.

  
   Real diode, the white band is the cathode                      Electrical symbol of the diode

           

            LEDs of various colors                        Internal scheme and symbol of the LED diode

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

The bipolar or BJT transistor is a component formed by two PN junctions (see figure below), it can be of the PNP type or of the NPN type, and it has three terminals called, Base (or Gate), Collector, Emitter (indicated in the electric symbol by an arrow) .
It was discovered in 1946 in the Bell telephone labs by researchers Walter Brattain, John Bardeen and William Schockley, they started modern electronics.
The transistor is an active component capable of amplifying the signals applied to it, such as the thermionic triode, but with many advantages, the main ones being that of being a solid state and therefore difficult to destroy mechanically, it is small if compared to tubes, it works with low voltages at the ends and its integration is relatively easy, moreover it does not require filament tension.
Very schematically, its operation can be defined thus, "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.
With the progress of the solid state component technique, other transistors optimized for some applications have been introduced, including the JFET (high input impedance), the MOSFET (switch with low resistance of the channel when directly polarized) and the UJT or unijunction (pulsed oscillator).
The transistors are enclosed in metal or plastic containers depending on the required power dissipation and the possible application of a heat sink.

              
      Internal scheme of BJT NPN transistor                  Symbol of the BJT NPN transistor
    
                     

    Power transistor with case TO220             Transistor for small signals in TO92 case


                                  
   
       Transistor inTO18 case                         2N3055 metallic power transistor in TO3 case

Finally, the monolithic integrated circuits are made by doping the areas of a semiconductor chip in a suitable way, in detail, by introducing more or less conductive impurities insulators or conductors (or resistors of the desired value) will be realized, P or N type impurities will realize transistors with the desired characteristics, by doing so you will obtain on a small semiconductor chip a complex circuit, accessible from the outside with terminals so as to be able to connect to the outside the components necessary for operation but not integrable (inductances, capacitors, resistors and other ).
There are analog and digital integrated circuits that perform very complex functions, it is thanks to them that electronic circuits have been miniaturized, with visible results by all, just think of tablets or smartphones, real miracles of electronic technology.
Integrated circuits built with normal components, without a container, are also produced, then enclosed in plastic containers and performing functions that are in any case simple, these types of components are called "hybrid integrated circuits". The STK series hybrid amplifiers are a very common example.

To know the characteristics of the active components, you must be in possession of the related datasheet.
The datasheets are information sheets, released by the manufacturer where it is possible to find all the information regarding the maximum and minimum parameters of the components' functioning, and even examples of realizations, an excellent site where to find datasheets of almost all the components can be found at this link .
Instead clicking with the mouse on this link you can view by way of example  the datasheet of a known component on the breach for many years, the strange low frequency amplifier TDA2003, capable of producing a dozen Watts, using few external components, you will also find in the datasheet the internal diagram of the component, and the examples of construction.

  
                Integrated circuit in D.I.P. case                       SMD integrated dual in line (DIL)

    
 
      Integrated circuit  5V negative regulator                Integrated circuit SMD flatpack

Of course it is impossible to condense all these concepts in a small space, mine wants to be only a good guide for those who look out on this fantastic world, it is possible however to deepen or request a professional consultation 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.