Electronic components form the basis of electronic products , understand the type , structure, properties commonly used in electronic components and can correct choice is to learn and master the basic electronic technology . There are commonly used in electronic components : resistors, capacitors, inductors, potentiometers , transformers , transistors , diodes , IC , etc., on the installation , the current can be divided into the traditional installation ( also known as through-hole mounted that DIP) and surface mount two class ( ie, also known as SMT or SMD).

Here Elinker electric sorting through information sharing and electronic components common knowledge that you choose :

a proper election has resistor values ​​and error:
Resistance selection : the principle is used with a nominal resistance of the resistor resistor values ​​required for the difference between the smaller the better.
Error Optional: error required time constant RC circuit resistor as small as possible , generally less than 5% optional for decoupling circuit , the feedback circuit filter circuit load circuit for error is not too high , 10% -20 % of the optional resistor devices .

b Note resistors limit parameters :
Rated voltage: when the actual voltage exceeds the rated voltage , even to meet the power requirements of the resistor will be breakdown.
Rated power: selected resistor power rating should be greater than the actual power to withstand more than twice in order to ensure long-term reliability resistor circuit working at .

c to preferred generic type resistor :
Universal resistor more categories , complete specifications, production volume, scope and range of resistance, appearance and shape , volume size has chosen to facilitate the procurement and maintenance.

d chosen according to the characteristics of the circuit :
High-frequency circuits: the smaller the better distribution parameters should be used metal film resistors, metal oxide film resistors and other high-frequency resistance .
Low-frequency circuits: wound resistors , carbon film resistors are applicable.
Power amplifier circuit , the bias circuit, sampling circuit : Circuit stability requirements are relatively high , should be selected temperature coefficient resistor .
Decoupling circuit, filter circuit : The change in resistance is not strictly required , resistors are applicable to any class .

e chosen according to the size of the circuit board resistance:

Sensitive resistors common sense:

a, thermistors:
Is an extremely sensitive resistor temperature , divided into positive and negative temperature coefficient temperature coefficient resistors, not only pay attention to the selection of its rated power, maximum operating voltage, nominal resistance , but also pay attention to the maximum operating temperature and resistance temperature factor and other parameters, and pay attention to the resistance change direction .

b, photoresistor :
With the intensity of light and the resistance to change resistor . , Into visible light-sensitive resistors, infrared light sensitive resistors, UV light-sensitive resistors, first determine the selection of the spectral characteristics of the circuit .

c, varistors :
Is sensitive to changes in the voltage non-linear resistor when the voltage across the resistor at a nominal value , the resistance value of the resistor was infinite state, when the voltage slightly higher than the nominal voltage, the resistance quickly decreased, so that the resistor is in a conducting state when the voltage is reduced to the nominal voltage or less , the resistance increased again .

Varistors into nonpolar ( symmetric ) and polar ( asymmetric ) varistor, the selection , the nominal varistor voltage value should be added to the voltage across the varistor 2 -2.5 times , and the other should pay attention to the pressure .
The temperature coefficient thermistor .

d, humidity resistance :
Is very sensitive to changes in humidity resistor, can be used in various humidity environments, it is converted into electrical signals and humidity transducer devices , the choice should be based on the different characteristics of different types of numbers and precision humidity resistors , humidity factor , response speed, etc. humidity range selection .

Note: The main characteristic resistance when in the low resistance characteristic is shown , but at higher frequencies , not only the resistance characteristics , also exhibit this side of reactance in the radio aspects ( especially important in the RF circuit ) .
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