An heuristic method oriented to compute the elements embedded into a positive feedback loop (PFL), is presented. The nullor concept is introduced first, in order to model the behavior of all active devices and controlled sources. From a nullor circuit, a congruence transformation is done in order to obtain a matrix called L, having an order 2N /spl times/ 2N, N as the number of nullors. By partitioning L, all the PFLs can be easily computed. Finally, the elements embedded into each PFL are obtained by searching for loops involving nullator-norator pairs, associated to the nullors forming a PFL computed from the matrix L.