Step Attenuator Calculator

A step attenuator is a precision resistor network used in RF and audio circuits to reduce signal strength in calibrated increments. Select your attenuator type (Pi, Tee, or Bridged-Tee), then enter your system impedance, attenuation in dB, number of steps, and step size into the Step Attenuator Calculator. You'll get the exact resistor values R1 and R2, plus total attenuation, input impedance, and output impedance for your design.

Ω
dB
dB

Results

R1 (Series/Shunt)

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R2 (Shunt/Series)

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Total Attenuation

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Input Impedance

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Output Impedance

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Results Table

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Frequently Asked Questions

What is the difference between Pi, Tee, and Bridged-Tee attenuators?

Pi attenuators use a series resistor with two shunt resistors to ground. Tee attenuators use two series resistors with one shunt resistor. Bridged-Tee is a modified Pi topology that maintains impedance matching while providing attenuation.

How do I choose the right system impedance for my attenuator?

Common system impedances are 50Ω for RF applications, 75Ω for video/cable systems, and 600Ω for audio applications. Match your attenuator impedance to your system's characteristic impedance.

What is the maximum practical attenuation for a single stage?

While theoretically unlimited, practical single-stage attenuators are typically limited to 20-40dB due to resistor tolerance and parasitic effects. Higher attenuation usually requires multiple stages.

How does step size affect attenuator design?

Smaller step sizes (0.5-1dB) provide finer control but require more switching positions. Larger steps (3-6dB) are simpler to implement but provide coarser adjustment. Choose based on your application's precision requirements.

What resistor tolerances should I use for accurate attenuation?

For precise attenuation, use 1% or better tolerance resistors. Critical applications may require 0.1% precision resistors. Higher tolerance resistors can cause impedance mismatch and inaccurate attenuation values.

Can stepped attenuators be used at high frequencies?

Yes, but parasitic capacitance and inductance become important at RF frequencies. Use low-inductance resistors, short connections, and consider transmission line effects above 100MHz.