Electronics Principles V11

Clive W. Humphris

ATTENUATORS: Attenuation.  

An attenuator is a simple circuit constructed entirely from resistors. The purpose of which is to reduce a signal level equally across all those frequencies present. This differs from a filter circuit, which allows a particular group of frequencies to pass through and attenuates others.

For the moment we are only interested in the input and output voltages to determine the degree of attenuation (measured in decibels as a ratio between the two voltages). An input of 10V and an output of 5V would be a loss of -6dB. Similarly, an input of 20V and an output of 10V would also have an attenuation or loss of -6dB.

The other consideration for attenuators is the input and output impedance, which may or may not be equal. This is important to ensure that there is a correct match between circuits for the maximum transfer of power. We will be introducing this feature later.

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