The current age, along with the stone and iron, can be called the SILICON age. It was this element that became the source of technological progress, because in any microcircuit there are tens, hundreds and even millions of transistors that consist of silicon. The appearance of semiconductors was predicted long before their appearance, since theoretically scientists came to this idea long ago, but in practice it was not possible to achieve ideal silicon purity. Now “Silicon Valley” (Silicon in Latin Silicium) is the most technologically advanced area in the world, and factories for the production of silicon for microcontrollers are in unprecedented technological purity.
It is the purity during production that makes it possible to achieve the effect of semiconductors; depending on the need, impurities are added to silicon (negligibly small amounts), which can be from group 3 (column) or group 5 (column) of the periodic table. Silicon itself is in group 4 and has 4 electrons in its outer orbit, if we add Indium (In group 3 there are 3 electrons), then we will get a deficiency of one electron or a HOLE, therefore it will be N-type, and the opposite when we add As( arsenic from group 5) we get a P-type semiconductor.
By combining these two types of silicon like a sandwich, we get a transistor with amazing properties.
A semiconductor device designed to change the parameters of current and voltage in a circuit.
There are many types of transistors, but the two most common are the pnp and npn transistor, which are displayed as a circle with a triangle, on one side of which there is an arrow showing the direction and therefore the type of pnp or npn transistor.
According to the European marking of transistors, the first character is the material (A-germanium, B-silicon, C-arsenide, R-cadmium sulfide), the second character is the type of transistor (C - low-power low-frequency transistor), the third character is a number from 100 to 999, series number product. In American markings, the first is a number that means the number of transitions (1-diode, 2-transistor, 3-teristor, 4-optocoupler), the second symbol is N, and on the new line we have a number from 100 to 9999 which means the product series. In addition to European and US markings, there are also Japanese and Domestic markings, which can be viewed in reference books.
Transistors are bipolar and field-effect. A bipolar transistor has three contacts:
Collector - we apply a strong current to it
Emitter - on it we receive current from the collector if the current of the required value is supplied to it
Base - control current is supplied to it
But the contacts of a field-effect transistor are called differently, drain (D) and source (S) (by analogy with bipolar - collector and emitter) the control contact is called gate (G)
A bipolar transistor is controlled by current, while mosfets (field-effect transistors) are controlled by voltage and no current flows between the control contact and the drain (emitter).
Checking the transistor with a multimeter
To check the transistor, you can use two devices (a multimeter and an LCR meter). Using a multimeter, we will check the transistor as two diodes that ring in one direction (indicate the voltage drop in millivolts) and do not ring in the other direction. If we have three contacts on a transistor, then we must make 6 measurements and only two will show any values, since checking in this way only indirectly shows serviceability, then a more modern way is to check using an LCR meter, which should show a schematic designation of the transistor , as well as its variety PNP or NPN, for bipolar transistors and pinout for field-effect transistors.
Since the field-effect transistor is controlled (opening and closing) using voltage, and the gate has, although very small, still a capacitance. Then, when voltage is applied to the gate of the field-effect transistor, it will open and remain in the open state until the capacitor has the required voltage.
When testing, any multimeter essentially supplies voltage to its probes from the internal battery, very often this voltage is enough to open the field-effect transistor, therefore we call it DRAIN and source, which do not ring, but if you apply voltage between the gate and source, then the transistor will open.