The resistance is an ordinary component, but there is a non-ordinary doorway. Our company has established since 1996, with decades of industry experience, now in order to organize industry secrets related to resistance, provide you with reference.
There are many parameters of the resistor, usually we generally pay attention to the resistance, accuracy, quota power, and these three indicators are suitable. It is true that in the digital circuit, we don’t have to pay attention to too many details. After all, there is only 1 and 0, and there is no more impact. However, in an analog circuit, when we use a precise voltage source, or when the signal is modulus, or an improved signal, the small changes in the resistance will bring a lot. When it is tapped with the resistor pound, of course, in the case of processing analog signals, the effect of the lower resistance parameter is analyzed according to the application of the analog circuit application.
The selection of the quota resistance of the resistor is often applied, such as a stream of LEDs, or sampling a current signal, and the resistance is basically no other option.
However, some occasions, there are a variety of choices for resistors, such as amplifying a voltage signal, as shown, the magnification of R2 is related to R2, and is independent of R2, R3.
At this time, the resistance of the selection resistor is still dependent: the larger the resistance resistance, the larger the thermal noise, the worse the performance of the amplifier; the smaller the resistance value is, the more work is, the greater the current noise, the larger the current noise, The worse the performance of the amplifier; this is a lot of amplifying circuits for dozens K, where there is a place to use large resistance, or use voltage followers, or use T-type networks to avoid.
The accuracy of the resistor is very good, not here. The accuracy of the resistor generally has 1% and 5%, precision 0.1%, etc. The price of 0.1% is about 1%, and the price of 1% is approximately 5%. Generally, the accuracy code A = 0.05%, b = 0.1%, C = 0.25%, D = 0.5%, f = 1%, g = 2%, J = 5%, K = 10%, m = 20%.
The power of the resistor is very simple, but it is often easy to use. For example, a 2512 patch resistor is 1W, depending on the specifications of the resistor, the temperature exceeds 70 degrees Celsius, the resistance is degraded.
2512 The patch resistor can be used to use a lot of power, at normal temperature, if the PCB pad does not have special heat dissipation, the temperature of the patch resistors of 2512 reaches 0.3W, the temperature may exceed 100 or even 120 degrees Celsius. At 125 degrees Celsius temperature, the amount of the 2512 power decrease is reduced to 30% depending on the temperature drop curve. This situation requires attention in any package resistance, do not superstitious nominal power, the key position is better, and then it is confirmed to avoid hidden dangers.
The resistance value of the resistor is generally less mention, especially novice, there is often no concept, thinking that the capacitor has a voltage resistant value. The voltage can be applied at both ends of the resistor, one is determined by the quota power, to ensure that the power does not exceed the amount of power, and the resistance is resistant to the resistance.
Although the power of the resistor does not exceed the amount of the power, the excessive voltage causes a fault such as a resistance to be unstable, and the resistance pin is climbed, and the reasonable resistance is selected according to the voltage used in use. Part of the pieces of packages include: 0603 = 50V, 0805 = 100 V, 1206 to 2512 = 200 V, 1 / 4W plug = 250V. Moreover, in the time application, the voltage on the resistor should be more than 20% compared with the amount with a voltage about the voltage. Otherwise, it will be prone to problems.
The resistance temperature coefficient is a parameter describing the resistance with temperature changes. This is determined by the material of the resistor. Generally, the package can be 100 ppm / ° C, which means that the resistance value changes by 25 degrees Celsius, meaning that the resistance value may vary from 0.25%. If it is 12 bit The ADC, 0.25% change is 10 LSBs.
So the AD620 is more than one resistor, and many older engineers will not be eager to use, they will use regular circuits to adjust the magnification through the proportion of two resistors, and when the resistance is the same type of resistance When the temperature caused by temperature causes changes to changes, the circuit is more stable.
In a higher precision instrument, it is easy to use metal film resistance, and their warm drifts are easy to do, of course, also expensive. In summary, in the precision application of the instrument class, the temperature coefficient is a very important parameter, and the resistance is not accurate can adjust the parameters at calibration, and the resistance cannot be controlled with the external temperature.
The structure of the resistor is more structure, here that it can be thought of. The starting resistance of the machine is generally used to precharge the large capacity of aluminum electrolysis with the resistor, and the relay relay is turned on the power supply after filled with aluminum electrolysis. This resistance requires impact resistance, it is preferred to use a large winding resistor, the amount of power is not important, but the instantaneous power is very high, and ordinary electrical resistance meets the requirements.
High voltage applications, such as electricity discharge resistance, actual operating voltage exceeding 500 V, preferably use high pressure glass glaze resistance rather than ordinary cement resistance. The application of spike absorption, such as both ends of the thyristor module need parallel RC to absorb, do DV / DT protection, preferably no inductive winding resistance, so that good absorption performance is good for spikes and is not easily damaged.
The above is a related introduction to "resistance and what data", more about "Frequency-sensitive varistor" can be viewed or online consultation through our website.