brief introduction: Attenuator is a kind of electronic components to provide attenuation, widely used in electronic equipment, its main purposes are :(1) adjust the size of the signal in the circuit; (2) in the comparative method measurement circuit, can be used to directly read the attenuation value of the measured network; (3) to improve impedance matching, if some circuits require a relatively stable load impedance, an attenuator can be inserted between the circuit and the actual load impedance, which can buffer