Use this tool to calculate resistor values for a T attenuator pad.
This attenuator type is used in Radio Frequency (RF) circuits as an alternative to a Pi configuration.
Enter
- desired value of attenuation
- the characteristic impedance
The default value of impedance is 50 ohm.
However it can be changed to any arbitrary value – for instance 75 ohm.
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
T Attenuator Resistor Table
| ATTENUATION (dB) | R1 (Ohm) | R2 (Ohm) |
| 1 | 2.9 | 433.3 |
| 2 | 5.7 | 215.2 |
| 3 | 8.5 | 141.9 |
| 4 | 11.3 | 104.8 |
| 5 | 14.0 | 82.2 |
| 6 | 16.6 | 66.9 |
| 7 | 19.1 | 55.8 |
| 8 | 21.5 | 47.3 |
| 9 | 23.8 | 40.6 |
| 10 | 26.0 | 35.1 |
| 11 | 28.0 | 30.6 |
| 12 | 29.9 | 26.8 |
| 13 | 31.7 | 23.6 |
| 14 | 33.4 | 20.8 |
| 15 | 34.9 | 18.4 |
| 16 | 36.3 | 16.3 |
| 17 | 37.6 | 14.4 |
| 18 | 38.8 | 12.8 |
| 19 | 39.9 | 11.4 |
| 20 | 40.9 | 10.1 |
| 21 | 41.8 | 9.0 |
| 22 | 42.6 | 8.0 |
| 23 | 43.4 | 7.1 |
| 24 | 44.1 | 6.3 |
| 25 | 44.7 | 5.6 |
| 26 | 45.2 | 5.0 |
| 27 | 45.7 | 4.5 |
| 28 | 46.2 | 4.0 |
| 29 | 46.6 | 3.6 |
| 30 | 46.9 | 3.2 |
| 31 | 47.3 | 2.8 |
| 32 | 47.5 | 2.5 |
| 33 | 47.8 | 2.2 |
| 34 | 48.0 | 2.0 |
| 35 | 48.3 | 1.8 |
| 36 | 48.4 | 1.6 |
| 37 | 48.6 | 1.4 |
| 38 | 48.8 | 1.3 |
| 39 | 48.9 | 1.1 |
| 40 | 49.0 | 1.0 |
| 41 | 49.1 | 0.9 |
| 42 | 49.2 | 0.8 |
| 43 | 49.3 | 0.7 |
| 44 | 49.4 | 0.6 |
| 45 | 49.4 | 0.6 |
| 46 | 49.5 | 0.5 |
| 47 | 49.6 | 0.4 |
| 48 | 49.6 | 0.4 |
| 49 | 49.6 | 0.4 |
| 50 | 49.7 | 0.3 |