# Attenuator Design Calculator

Radio frequency (RF) circuits require attenuators to limit the amount of power

• Out of a Transmitter

Attenuators can be constructed from resistors and the value of the resistors determine the reduction in signal level measured in dB (deciBels).

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

### 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