GFTs, General Feedback Theorem, dual current/voltage injection. loop gain only

GFT summary, GFT manual
In this analysis
(actual GFTtime.SCP file), a behavioral multiplexer is used within a subcircuit named Xgft to reconfigure the null parameters for each of the 3 Transient simulations needed to measure the principal loop gain.  The time domain solution takes considerably longer than its AC analysis counterpart, GFTs, This script runs with the GFTt and GFTt2 models. To make the script work in a general sense, it is necessary for the user to ALWAYS name the GFTs model Xgft. The GFTs model is a simplification of the more general case. It is used to get an accurate measure of a control system loop gain, even when the loop cut or injection point experiences significant loading.

Other simulation templates for the GFT include GFTE, GFTEE, GFTJ, GFTJJ, GFTS and GFT