Calculating PCB Track Impedance FormulasCalculation of PCB Track Impedance by Andrew J Burkhardt, Christopher S Gregg and J Alan Staniforth T he use of high-speed circuits requires PCB tracks to be designed with controlled (characteristic, odd-mode, or differential) impedances. Wadell[1] is one of the most comprehensive sources of equations for evaluating these impedances. This source includes many configurations including stripline, surface microstrip and their coplanar variants. The IPC publication, IPC-2141[2], is another source of equations, but has a smaller range of configurations, similar to those presented in IPC-D-317A. However, for some configurations there are differences between the equations given in these publications. The authors believe that it is now opportune to examine the origin of the equations and to Figu……