by Chuck McGregor
Resistive L-Pad and Step Attenuator Calculator
The link takes you to an Excel VB program that calculates resistive attenuators balanced and unbalanced L-pads and step attenuators up to 30 steps. Most importantly, it accounts for the load on the attenuator. It requires entering just 4 basic values. The trick with resistive attenuators is to keep the aggregate load (attenuator plus load impedance) on the source at least 10 times the source impedance. Manually calculating simple L-pads and especially step attenuators to meet this condition can be, in a word, challenging. This program does it for you. As an example the program will instantly design a 12 step, 2.7 dB per step, 50k ohm attenuator feeding a 5k ohm input changing the aggregate load on the source by only 500 ohms to 4.5k ohm. Doing this manually would take more than a few minutes!