A semiconductor electronic element with an input signal creates, amplifies, and modifies pulses in integrated circuits and systems for storing, processing, and transmitting information. A transistor is a resistance whose function is regulated by the voltage between emitter and base or source and gate, depending on the type of module.
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Types of Transistors
Transistors are widely used in the manufacture of digital and analog ICs to zero out static consumer current and obtain improved linearity. Types of transistors differ in that some are controlled by changes in voltage, while others are controlled by current deviation.
Fieldbus modules operate at higher DC resistance, transforming at high frequency does not increase the energy cost. If we say what a transistor is in simple words, it is a module with a high gain edge. This characteristic of the field types is greater than that of the bipolar types. The former have no charge carrier dissipation, which speeds up operation.
Field semiconductors are used more often because of advantages over bipolar types:
- powerful resistance at the input at constant current and high frequency, it reduces the energy loss for control;
- Absence of buildup of nonessential electrons, which speeds up the transistor's operation;
- transport of mobile particles;
- stability under temperature fluctuations;
- Low noise due to lack of injection;
- Low power consumption during operation.
Types of transistors and their properties determine the purpose. Bipolar type transistor heating increases the current along the path from collector to emitter. They have a negative resistance coefficient and the moving carriers flow to the collector from the emitter. The thin base is separated by p-n junctions, and current occurs only when moving particles accumulate and inject them into the base. Some charge carriers are captured by the adjacent p-n junction and accelerated, so the parameters of the transistors are calculated.
Field effect transistors have another kind of advantage, which should be mentioned for dummies. They are connected in parallel without any resistance equalization. Resistors are not used for this purpose, because the value grows automatically as the load changes. To obtain a high switching current value, a complex of modules is recruited, which is used in inverters or other devices.
Bipolar transistor should not be connected in parallel, the determination of functional parameters leads to the fact that the thermal breakdown of an irreversible nature is detected. These properties are related to the technical qualities of simple p-n channels. Modules are connected in parallel using resistors to equalize the current in the emitter circuits. Depending on the functional features and individual specifics in the classification of transistors are distinguished bipolar and field effect types.
Bipolar Transistors
Bipolar designs are manufactured as semiconductor devices with three conductors. Each of the electrodes includes layers with hole p conductivity or impurity n conductivity. The choice of layer configuration determines the release of p-n-p or n-p-n types of devices. When the device is turned on, different types of charges are simultaneously carried by holes and electrons, 2 types of particles are involved.
Carriers move due to the mechanism of diffusion. Atoms and molecules of the substance penetrate the intermolecular lattice of the neighboring material, after which their concentration is equalized throughout the volume. The transfer is made from areas with high compaction to places with low content.
Electrons also propagate under the action of the force field around the particles when the alloying additives are unevenly incorporated into the base mass. To speed up the action of the device, the electrode connected to the middle layer is made thin. The edge conductors are called the emitter and collector. The reverse voltage characteristic of the junction is unimportant.
Field Effect Transistors
A field-effect transistor controls resistance by means of an electric transverse field arising from the applied voltage. The place from which electrons move into the channel is called the source, and the drain looks like the end point of charge entry. The control voltage travels through a conductor called the gate. Devices are divided into 2 types:
- with a control p-n junction;
- TIR transistors with isolated gate.
The first type contains a semiconductor wafer, which is connected to the controlled circuit with electrodes on opposite sides (drain and source). A different kind of conductivity occurs after the plate is connected to the gate. A DC bias source inserted into the input circuit produces a locking voltage at the junction.
The source of the amplified pulse is also in the input circuit. After the input voltage is changed, the corresponding index at the p-n junction is transformed. The layer thickness and cross-sectional area of the channel junction in the crystal that allows the flow of charged electrons is modified. The width of the channel depends on the space between the depletion region (under the gate) and the substrate. The control current at the start and end points is controlled by changing the width of the depletion region.
The TIR transistor is characterized by the fact that its gate is isolated from the channel layer. In the semiconductor crystal, called the substrate, doped sites with opposite sign are created. They have conductors - the drain and the source, between which there is a dielectric at a distance of less than a micron. The metal electrode - the gate - is placed on the insulator. Because of the resulting structure, containing metal, dielectric layer and semiconductor, transistors are assigned the abbreviation TIR.
Design and principle of operation for beginners
Technologies operate not only with a charge of electricity, but also with a magnetic field, light quanta and photons. The principle of operation of the transistor lies in the states between which the device switches. Opposite small and large signal, open and closed state - this is the dual operation of the devices.
Along with the semiconductor material in the composition, used in the form of a single crystal, doped in some places, the transistor has in its design:
- metal leads;
- dielectric insulators;
- Transistor housing made of glass, metal, plastic, metal-ceramic.
Before the invention of bipolar or polar devices, electronic vacuum tubes were used as active elements. The circuits developed for them, after modification, are used in the production of semiconductor devices. They could be connected as a transistor and applied, since many of the functional characteristics of the tubes are suitable in describing the operation of field types.
Advantages and disadvantages of replacing lamps with transistors
The invention of transistors is a stimulus for the introduction of innovative technology in electronics. Modern semiconductor elements are used in the network, compared with the old tube circuits such developments have advantages:
- Small size and light weight, which is important for miniature electronics;
- possibility to apply automated processes in the production of devices and group the stages, which reduces the cost;
- Use of small-sized current sources due to the need for low voltage;
- instantaneous activation, no need to heat up the cathode;
- Increased energy efficiency due to lower power dissipation;
- ruggedness and reliability;
- smooth interaction with additional elements in the network;
- resistance to vibration and shock.
The disadvantages are manifested in the following provisions:
- Silicon transistors do not function at voltages greater than 1 kW; lamps are effective at values greater than 1-2 kW;
- when using transistors in high-power radio broadcasting networks or UHF transmitters, the matching of low-power amplifiers connected in parallel is required;
- vulnerability of semiconductor elements to electromagnetic signal;
- sensitive response to cosmic rays and radiation, requiring the development of radiation-resistant microcircuits.
Switching Schemes
To operate in a single circuit, a transistor requires 2 input and output pins. Almost all types of semiconductors have only 3 connection points. To get out of the predicament, one of the ends is designated as common. Hence 3 common wiring schemes follow:
- For a bipolar transistor;
- polar device;
- with an open drain (collector).
The bipolar unit is connected with a common emitter for both voltage and current amplification (OE). In other cases, it matches the pins of a digital chip when there is a large voltage between the external circuit and the internal connection plan. This is how the common-collector connection works, and there is only an increase in current (OK). If a voltage increase is needed, the element is introduced with a common base (CB). The variant works well in composite cascade circuits, but is rarely used in single-transistor designs.
Field semiconductor devices of the TIR and p-n junction varieties are included in the circuit:
- with common emitter (SI) - a connection similar to that of a bipolar module
- with common output (OC) - connection similar to OC type
- with joint gate (JG) - similar to OB description.
In open-drain plans, the transistor is included with a common emitter as part of the chip. The collector pin is not connected to other parts of the module, and the load goes to the outer connector. The choice of voltages and collector currents intensity is made after the project installation. Open drain devices work in circuits with powerful output stages, bus drivers, and TTL logic circuits.
What are transistors for?
The application is differentiated depending on the type of device - bipolar module or field device. Why are transistors needed? If low amperage is needed, such as in digital plans, field-effect types are used. Analog circuits achieve high gain linearity over a wide range of supply voltages and output parameters.
Applications for bipolar transistors include amplifiers, combinations thereof, detectors, modulators, transistor logic circuits, and logic-type inverters.
The applications of transistors depend on their characteristics. They operate in 2 modes:
- In amplifying regulation, changing the output pulse with small deviations of the control signal;
- in the key order, controlling the power of loads when the input current is weak, the transistor is fully closed or open.
The type of semiconductor module does not change its operating conditions. The source is connected to a load such as a switch, a sound amplifier, a lighting fixture, it could be an electronic sensor or a high-power adjacent transistor. The current starts the operation of the load device, and the transistor is connected in the circuit between the unit and the source. The semiconductor module limits the amount of power going to the unit.
The resistance at the output of the transistor is transformed according to the voltages on the control conductor. The current and voltage at the beginning and end of the circuit varies and increases or decreases and depends on the type of transistor and how it is connected. Controlling the controlled power supply leads to an increase in current, a pulse of power, or an increase in voltage.
Both types of transistors are used in the following applications:
- In digital regulation. Experimental designs of digital amplifier circuits based on digital-to-analog converters (DACs) have been developed.
- In pulse generators. Depending on the type of unit, the transistor operates in key or linear order to reproduce rectangular or arbitrary signals, respectively.
- In electronic hardware devices. To protect information and programs from theft, illegal tampering and use. The operation takes place in key mode, the current is controlled in analog form and regulated by the pulse width. Transistors are put in electric motor drives, pulse voltage stabilizers.
Monocrystalline semiconductors and modules for opening and closing circuits increase power, but function only as switches. Digital devices use field-type transistors as cost-effective modules. Manufacturing techniques in the concept of integrated experiments involve producing transistors on a single silicon chip.
Miniaturization of crystals leads to faster computers, less energy and less heat generation.
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