2. Fixed resistor selection
There are many types of fixed resistors, and the choice of which material and structure of the resistor, the circuit should be based on the specific requirements of the application.
(1) Nominal values of the selected resistors should be close to those calculated in the circuit design. General circuit using the allowable error of +5% to +10% of the resistors. Special circuits and precision instruments used in the resistors, should be allowed to use small precision resistor.
(2) high-frequency circuit can not use wirewound resistors, should be used in distributed inductors and distributed capacitance of small non-wirewound resistors, such as carbon film resistors, metal film resistors and metal oxide film resistors.
(3) small-signal high-gain amplifier circuit should be used low-noise resistors, such as metal film resistors, wirewound resistors, can not use the larger sound of synthetic carbon film resistors and organic solid resistors.
(4) The rated resistance of the selected resistor should meet the requirements of the resistor in the circuit. The resistors used in larger power circuits can have a rated power that is more than twice the calculated value of the actual circuit power. Some require long-term work in the high temperature environment of the resistor, you can use metal oxide film resistors or wirewound resistors.
(5) wire wound resistor current noise, power, high temperature, but larger. Common wirewound resistors are commonly used in low-frequency circuits or as current limiting resistors, voltage divider resistors and bleeder resistors. High-precision wirewound resistors used for resistance boxes, fixed attenuators and a variety of sophisticated electronic instruments.