Attenuators and filters
Noel M. Morris · 1996
An attenuator reduces the magnitude of the voltage or current entering its terminals by the a constant amount at all frequencies , and is usually constructed using pure resistors. Attenuators (or attenuator pads) are used, for example, at the input of an electronic instrument in order to reduce a voltage or current to a value which can be handled by the instrument. A filter is a circuit which attenuates certain frequencies, whilst allowing others to pass with very little attenuation. Whilst we can specify the numerical amount of attenuation introduced by an attenuator or filter, the attenuation is usually expressed in decibels (dB), which is a logarithmic ratio.