Common sense of electronic component selection

At present, the common sense of electronic component selection is more and more widely used in modern times. It is worth learning. Now we will have a deep understanding of the common sense of electronic component selection.

a. Correctly select the resistance value and error of the resistor:

Selection of resistance value: The principle is that the smaller the difference between the nominal resistance value of the resistor used and the required resistance value, the better.

Error selection: the error of the resistor required by the time constant RC circuit should be as small as possible, generally within 5%. For decoupling circuit and feedback circuit filtering circuit, the load circuit does not require too much error, and 10% – 20% resistors can be selected.

b. Note the limit parameters of the resistor:

Rated voltage: when the actual voltage exceeds the rated voltage, even if the power requirements are met, the resistor will also be damaged by breakdown.

Rated power: the rated power of the selected resistor should be more than twice of the actual power to ensure the reliability of the resistor in the circuit for long-term operation.

C. General purpose resistors are preferred:

There are many types, complete specifications and large production batches of general-purpose resistors, and there is room for selection of resistance value range, appearance shape and volume size, which is convenient for procurement and maintenance.

d. Select according to the circuit characteristics:

High frequency circuit: The smaller the distribution parameters, the better. High frequency resistors such as metal film resistor and metal oxide film resistor should be selected.

Low frequency circuit: both winding resistance and carbon film resistance are applicable.

Power amplifier circuit, bias circuit, sampling circuit: the circuit requires high stability, and the resistor with small temperature coefficient should be selected.

Decoupling circuit and filtering circuit: there is no strict requirement for resistance value change, and any type of resistor is applicable.

e. Select the resistance according to the size of the circuit board:

2、 Common sense of sensitive resistor

A. Thermistor:

The resistance element is a kind of resistor that is very sensitive to temperature. It is divided into positive temperature coefficient resistor and negative temperature coefficient resistor. When selecting, we should pay attention not only to its rated power, maximum working voltage, nominal resistance value, but also to its maximum working temperature, resistance temperature coefficient and other parameters, and pay attention to the direction of resistance value change.

b. Photoresistor:

A resistor whose resistance varies with the intensity of light, It is divided into visible light photoresist, infrared light photoresist and ultraviolet light photoresist. The spectral characteristics of the circuit shall be determined before selection.

c. Varistor:

It is a nonlinear resistor that is very sensitive to voltage changes. When the voltage on the resistor is within the nominal value, the resistance value on the resistor is infinite. When the voltage is slightly higher than the nominal voltage, the resistance value drops quickly, making the resistor in the conduction state. When the voltage decreases below the nominal voltage, the resistance value starts to increase again.

Varistors can be divided into non-polar (symmetric) and polar (asymmetric) varistors. When selecting, the nominal voltage value of the varistor should be 2-2.5 times of the voltage applied to both ends of the varistor. In addition, pay attention to the voltage.

Temperature coefficient of sensitive resistor

d. Humidity sensitive resistor:

It is a resistor that is very sensitive to humidity changes and can be used in various humidity environments. It is a transducer that converts humidity into electrical signals. It should be selected according to the different characteristics of different types of numbers and the precision, humidity coefficient, response speed, humidity range, etc. of the humidity sensitive resistor.

Note: The main characteristic of resistance in low frequency is resistance characteristic, but in high frequency, it not only shows resistance characteristic, but also shows reactance characteristic, which is particularly important in radio (RF circuit).

To sum up, this article has explained the common sense of electronic component selection. I believe that everyone has a deeper understanding of the common sense of electronic component selection. I hope this article can be of great reference value to all readers.