Pi Attenuator Circuit
The Pi-pad attenuator is so called because its design resembles that of the Greek letter pi ( π ) meaning that it has one series resistor and two parallel shunt resistors to ground at the input and the output. The Pi-pad attenuator is another fully symmetrical purely resistive network that can be used as a fixed attenuator between equal impedances or for impedance matching between unequal impedances.
Enter A, Zi and Zo (all three are required) to calculate R1, R2 and R3.