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dB Attenuator Calculator

To use this tool, enter the desired value of dB attenuation and the characteristic impedance (default value is 50 ohm). The tool computes resistor values in different configurations:

  • Pi Attenuator
  • T Attenuator

Pi Attenuator Calculator

Pi Attenuator

Formula

R1 = Zo [10dB/20 + 1] / [10dB/20 – 1]

R2 = Zo/2 [10dB/10 – 1] / [10dB/20]

where R1 is the shunt resistor (to ground) and R2 is the series resistor. To build this attenuator you will need

  • two shunt resistors – one at the input and the other at the output
  • one series resistor

T Attenuator Calculator

Formula

R1 = Zo [10dB/20 – 1] / [10dB/20 + 1]

R2 = (2*Zo)*[10dB/20] / [10dB/10 – 1]

where R1 is the series resistor and R2 is the shunt resistor (to ground). To build this attenuator you will need

  • two series resistors – one at the input and the other at the output
  • one shunt resistor