The gain formula is as follows:
$$G = \frac{y_\text{out}}{y_\text{in}} = \frac{ \sum_{k=1}^N {G_k \Delta _k} }{ \Delta\ }$$
$$\Delta = 1 - \sum L_i + \sum L_iL_j- \sum L_iL_jL_k + \cdots + (-1)^m \sum \cdots +\cdots$$
where:
- Δ = the determinant of the graph.
- yin = input-node variable
- yout = output-node variable
- G = complete gain between yin and yout
- N = total number of forward paths between yin and yout
- Gk = path gain of the kth forward path between yin and yout
- Li = loop gain of each closed loop in the system
- LiLj = product of the loop gains of any two non-touching loops (no common nodes)
- LiLjLk = product of the loop gains of any three pairwise nontouching loops
- Δk = the cofactor value of Δ for the kth forward path, with the loops touching the kth forward path removed.
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