T pad

The topology of an attenuator circuit will usually follow one of the simple filter sections.

However, there is no need for more complex circuitry, as there is with filters, due to the simplicity of the frequency response required.

Circuits are required to be balanced or unbalanced depending on the geometry of the transmission lines they are to be used with.

For audio and telecommunications, balanced circuits are usually required, such as with the twisted pair format.

However, it can be converted to a balanced circuit by placing half the series resistances in the return path.

The values of resistance of the attenuator's elements can be calculated using image parameter theory.

Figure 1. Schematic circuit of a T-pad attenuator.
Figure 2. A general L-section circuit with series impedance Z and shunt admittance Y .
Figure 3. A T-pad attenuator formed from two symmetrical L sections. Because of the symmetry, R 1 = R 3 in this case.