Attenuator

An attenuator is a passive electronic device that reduces the amplitude of a signal without significantly distorting its waveform, while presenting a specified input and output impedance. In matched systems, it preserves impedance continuity to minimize reflections and ensure predictable performance. Attenuation is typically specified in decibels (dB); for a matched system, a 20 dB attenuation reduces the signal voltage to one-tenth of its original value (and the power to one-hundredth).

There are fixed and adjustable types. A fixed attenuator provides a specific attenuation value and is often built as a resistive pad network. Variable attenuators allow control over the attenuation level, either by a knob, switch, or digital control, and are common in test equipment and communication links. Common pad topologies used to realize attenuators include L-pad, T-pad, and Pi-pad configurations, chosen to achieve the desired impedance and attenuation across the frequency range.

Applications span radiofrequency, microwave, instrumentation, and audio domains. In RF and microwave systems, attenuators protect receivers, calibrate systems, or set signal levels while maintaining impedance matching. In audio and instrumentation, they prevent overload, enable level matching, or serve as adjustable gain controls in a passive form. Power handling, frequency response, and compression or thermal effects are important design considerations; higher-frequency and higher-power designs require attention to parasitics, return loss, and heat dissipation.

Attenuators are distinct from amplifiers; they reduce signal strength without increasing it, and they are often used in conjunction with amplifiers or receivers to achieve safe, accurate operation.