Hey friends, welcome to the kohiki All About ELECTRONICS & ELECTRICITY. In this article, we will learn about the RESISTOR PROPERTIES & types
- RESISTOR PROPERTIES
RESISTOR PROPERTIES It is the job of the resistor to resist the flow of electricity in the circuit. Hence their primary parameter is the resistance value. Adequate preparation tolerance should be selected for each specific application. The final resistance value may deviate from the specification for a number of reasons. One is the resistance temperature coefficient or TCR, which is often specified for precise applications.
Stability defines long-term variations of resistance. After a long period of electrical load, the resistance value does not return to its original value. Electric noise appears on each resistor and is for low-noise amplifying applications.
RESISTOR PROPERTIES For high-frequency applications, inductance and capacitance characteristics play a role. Next to the characteristics related to the resistance value, the maximum power and voltage can be specified. Maximum power rating(resistor symbol” “resistor diagram” “wire-wound resistor”) For power electronics, resistors on electronic circuit boards often do not reach the maximum power rating. For high voltage circuits, the maximum rated voltage must be taken into account. The quality of the resistor is more important for some applications than others in terms of durability and reliability
Measured in ohms, the resistance of a resistor depends on its material and shape. Some materials have high resistance, resulting in high value. For a detailed overview of resistivity, see Chapter The resistance value is often printed on the resistor with a number or in the form of a color code.
The power rating of the resistor defines the maximum power dissipated by a resistor (safely). As stated in Joule’s first law, the electric power generated is related to voltage and current(RESISTOR PROPERTIES)
When the electrical energy is equal to the heat emitted (by radiation, convection and convection), the temperature (“how are resistors made” “what does a variable resistor do in a circuit”)of the resistor is stabilized. The temperature is not uniform across the resistor. The resistor is slightly hotter than the body terminals, with the highest temperature in the center of the body. (RESISTOR PROPERTIES)The higher the heat dissipation rate to the environment, the lower the temperature rise. Larger resistors with a larger surface area usually dissipate heat at a higher rate. If (average) energy dissipation
Larger than the power rating, the resistor may be damaged. It can have many consequences. The resistance value may change permanently, the lifetime may be significantly reduced or the component may be completely damaged, resulting in an open circuit. (RESISTOR PROPERTIES)In extreme cases, high power can also cause a fire. Special flameproof resistors are available that can cause a circuit brake before the temperature reaches a dangerous level. The power rating of the resistor defines the maximum power dissipated by a resistor (safely).
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The nominal energy rating is defined for a given ambient temperature in free air. In practice, the amount of power dissipated without damaging a resistor is strongly dependent on the operating conditions and is therefore not equal to the nominal power rating. For example, (RESISTOR PROPERTIES)a high ambient temperature can significantly lower the energy rating. This effect is called directing.
This should be taken into account by the designer. Often electrical power is chosen to be greater than electrical energy. Resistors are usually rated at a temperature of 70 C and begin to derail above this resistor. (characteristics of capacitor” “resistance parameter” “characteristics of the inductor)This means that the resistor can only use a reduced power level above this temperature. This is explained by the derating curve.
Resistor Derating Chart – Indicates the nominal rating percentage for a given ambient temperature on the horizontal axis. (RESISTOR PROPERTIES))In this case, the full power rating of the resistor is given up to 70 C. Aside from the effect of ambient temperature, there are many other factors that affect dehydration. The most important points are described below.
- The heat loss rate is limited by installing a resistor in the premises. The enclosure limits airflow and therefore heat can be removed by convection. Radiated heat is removed at a low rate because the enclosure walls act as a thermal barrier. (RESISTOR PROPERTIES)The environmental effect on the heat loss rate depends strongly on the size, shape, orientation, material, and wall thickness. It is difficult to predict how these parameters will affect the temperature rise.
- Increasing heat transfer by forced convection allows for higher watt dissipation than normal natural convection. This can be achieved by creating airflow or liquid cooling.(RESISTOR PROPERTIES)
- Some resistors are designed by handling air fins, forming a large surface to dissipate heat.
- The resistors on the circuit board are often close to each other. The thermal radiation of a resistor is received by the next resistor and therefore there is an additional increase in temperature for given power consumption.
- Resistors release heat through convection and radiation. As air density decreases, convection also decreases. Convection over a distance of more than 30 km was very low, with only heat dissipation by radiation.
For most electronic circuits, the power rating is not a key parameter because those resistors emit a small amount of power of one watt or less. In power electronics, the power rating is an important feature. Usually spoken here when power ratings are one watt or more. Common applications include power supplies, dynamic brakes, power-switching circuits, power amplifiers, and heaters.
Inductance is the electrical property of conductors through which current flows through a conductor, inducing electromotive force in the conductor itself (self-inductance) and other nearby conductors.(RESISTOR PROPERTIES) Because resistors are made of conductive materials, they also exhibit inductance as an unwanted, parasitic effect.
This effect is especially noticeable if the resistor is made of coil-shaped wire. Depending on the application, especially in DC circuits, the resistor inductance(“properties of conductor” “metal film resistor” “resistors color code”) can be easily overlooked. However, parasitic inductance is an important factor in high-frequency frequency AC applications. The reason for this is that the impedance of the resistor increases with the frequency of the applied voltage due to its reaction increase.
INDUCTORS AND RESISTORS
Electrical loads can be divided into two types: real (or resistive) loads and reactive loads. Real loads are used to convert electrical energy into heat. The ideal resistor is a fully resistive load, i.e. all the electrical energy applied to the resistor dissipates like heat. Reactive loads, on the other hand, convert electrical energy into a magnetic or electric field and temporarily store it before returning it to the rest of the circuit. (RESISTOR PROPERTIES)Reactive loads can be inductive or capacitive. The inductive load-store store’s energy in the form of a magnetic field, while capacitive loads store energy in the form of an electric field.
The main difference between ideal resistors and ideal inductors is that resistors dissipate electrical energy like heat, while inductors convert electrical energy into a magnetic field. The ideal resistors have a zero reaction and the result is zero inductance. (RESISTOR PROPERTIES) Unfortunately, electrical devices are not ideal in practice and even simple resistors have a slight parasite inductive reaction.
Resistors are used when a fully resistive load is required, so inductance is often an unwanted side effect and in this case, it is called “parasite inductance”. All true resistors exhibit more or less parasitic excitation depending on the design and structure of the resistor. Parasitic inductances in the AC circuit can cause unwanted coupling between system blocks or delay the circuit response at high frequencies.
The source of inductance problems may be self-inductance, which can also be observed when the resistor is away from other conductors or away from mutual inductance, which can be observed near other high-frequency devices. (RESISTOR PROPERTIES)Self-stimulation distorts the signal at high-frequency encyclopedias, while the mutual stimulus signal introduces noise along the path. Helical wire wound resistors contain significant parasitic stimuli, especially due to the coil shape. Resistors made of the metal film are specially designed for the use of high-frequency agencies windings to avoid creating coil shape and reducing parasite excitation.
Capacitance is the body’s ability to store electrical energy Form of electric charge. Practical resistors always display Capacitance as a parasitic property. Depending on the application, Resistor capacitance can easily be ignored in DC Circuits. In some applications, such as snubber resistors, the Capacitive parasitic effect is actually a desirable effect.
On the other hand Hand, parasitic resistance capacity is an important factor in High-frequency AC applications, creating an unwanted effect. The reason for this is that it increases with the (RESISTOR PROPERTIES)impedance of the resistor Frequency of the applied voltage frequency due to its reaction increase. The higher the frequency, the lower the impedance The resistor is no longer observed as a static element High-frequency encies virtues and becomes a frequency-based element.
CAPACITORS AND RESISTORS
Electrical loads can be divided into two types: real (or resistive) loads and reactive loads. Real loads are used to convert electrical energy into heat. The ideal resistor is a fully resistive load, i.e.(RESISTOR PROPERTIES) all the electrical energy applied to the resistor dissipates like heat. Reactive loads, on the other hand, convert electrical energy into a magnetic or electric field and temporarily store it before returning it to the rest of the circuit.
Reactive loads can be inductive or capacitive. The inductive load-store stores energy in the form of a magnetic field, while capacitive loads store energy in the form of an electric field. The main difference between ideal resistors and ideal capacitors is that resistors dissipate electrical energy like heat, while capacitors convert electrical energy into the electric field. Ideal resistors have a zero reaction and as a result, their capacitance becomes zero. (RESISTOR PROPERTIES)Unfortunately, electrical devices are not ideal in practice and even simple resistors have a slight parasitic capacitive reactivity.
Resistors are used when a fully resistive load is required, so Capacitance is often an unwanted side effect and in this case it is Called “parasite capacitance”. All true resistors exhibit parasite More or less capacitance depending on the design And resistor structure.
Parasitic capacitances in AC The circuit causes unwanted coupling between system blocks, or Delays at high frequencies can cause a circuit response. (RESISTOR PROPERTIES)There are resistors specially designed for use at high-frequency encies, These are advertised as low capacitance resistors, but accurate Capacitance statistics are hard to find in datasheets.
CAPACITANCE OF DIFFERENT RESISTORS
As mentioned earlier, manufacturers rarely make available Typical capacitance values for their resistors. As a general rule, SMD (Surface-mounted) contains fewer parasites than resistors Hole resistors. There is also an explanation Ideal conductors have a certain capacity under ideal conditions Store charge. (RESISTOR PROPERTIES)The metal leads that connect the resistor to the rest The circuit is an example of such a conductor. The longer Leeds, the higher the charge can be stored, and the higher the parasitic capacitance. Therefore, low leads, low parasitic effects can be seen in a Given resistor, hence SMD resistors have less parasitic effects.
If low capacitance is desired, the resistor should be kept small And as compact as possible. Wire-wound inhibitors should be avoided Because the windings produce inter-coil capacitance, which it does Use above 50 kHz.
Up to carbon type resistors are useful at Approximately 1 MHz. Foil resistors, on the other hand, are superior Characteristics for high-frequency frequency use, usually with capacitance Less than 0.05 pF, which allows them to withstand up to a dozen frequencies 100 MHz.As mentioned earlier, manufacturers rarely make available Typical capacitance values for their resistors. (RESISTOR PROPERTIES)As a general rule, SMD (Surface-mounted) contains fewer parasites than resistors Hole resistors.
There is also an explanation Ideal conductors have a certain capacity under ideal conditions Store charge. The metal leads that connect the resistor to the rest The circuit is an example of such a conductor. The longer Leeds, the higher the charge can be stored, and the higher the parasitic capacitance. (RESISTOR PROPERTIES)Therefore, low leads, low parasitic effects can be seen in a Given resistor, hence SMD resistors have less parasitic effects. If low capacitance is desired, the resistor should be kept small And as compact as possible.
Wire-wound inhibitors should be avoided Because the windings produce inter-coil capacitance, which it does Use above 50 kHz. Up to carbon type resistors are useful at Approximately 1 MHz. (RESISTOR PROPERTIES)Foil resistors, on the other hand, are superior Characteristics for high-frequency frequency use, usually with capacitance Less than 0.05 pF, which allows them to withstand up to a dozen frequencies 100 MHz.
APPLICATIONS WHERE PARASITIC EFFECTS PLAY A ROLE
Parasitic effects are most prominent at high frequencies. For example, a metal foil 1 kΩ resistor at 100 MHz behaves as a 1.001 kΩ resistor, considering the effects of all parasites. This is an example of a good frequency response to a resistor. For comparison, wire wound resistance is only used up to 50 kHz due to inductive and capacitive parasitic effects. Even when bifilar (non-inductive) winding methods are used, the intercoil capacitance limits the maximum usable frequency.
Some applications that are particularly sensitive to parasitic effects are high-frequency amplifier circuits, GHz clock generators, microwave circuits, and so on. An example of a circuit that takes advantage of a capacitive parasite effect is the snubber resistor used to protect switching elements (switches and thyristors) from voltage spikes generated by inductive loads such as electric motors during current cut-offs. These are most often made of bifilar wire wound resistors to reduce inductance.
For snubber applications, resistors are designed so that the capacitance is in series with the resistor, not parallel to the standard parasite capacitance.
THERMAL AND CURRENT NOISE
There are two types of noise: thermal noise and current Noise. To understand their principle, they will be discussed further Details. In all matters, electrons move permanently. As the temperature rises, the motions increase. Vibrations of Electrons carry an electrical signal (AC) across the terminals Part. (RESISTOR PROPERTIES)Since the vibrations are completely random, the Electrical signal noise.
This is called thermal noise or Johnson noise. This is the main reason for the noise of the resistors. Thermal noise The broad frequency is constant over a range of frequencies. The current noise, however, Decreases as the frequency increases. Thermal noise increases With a larger resistance value, the current noise decreases.
In each amplifier circuit, the input resistor is critical. Any noise at The input signal is amplified to full gain. (RESISTOR PROPERTIES) Hence It is of high importance to choose low-noise insulation in the first stage As well as low resistance value.
However, it is not valid for load Resistor, from the gain obtained from the high resistance value Exceeds high noise level. Because of the thermal noise Depending on the temperature, it is very effective to cool the input steps To reach low noise performance
So, I hope in this Article you understood what is RESISTOR PROPERTIES & types, how it works, and what are the different types of RESISTOR PROPERTIES & types. So, if you have any questions or suggestions, do let me know here in the comment section below.
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