Stabilisation of multi‐loop amplifiers using circuit‐based two‐port models stability analysis

This article applies a systematic approach based on the normalized determinant function (NDF) theory to analyse stability in multi-loop circuits and design required stabilization network. Presenting several provisions, return ratios are extracted by employing immittance or hybrid matrices (Z, Y, G H) of active two ports. Using these matrices, instead S-parameters, facilitates selection an appropriate stabilizer As practical case, non-uniform distributed amplifier (NDA) is designed inspected for potential instabilities. The presented procedure detects instability associated with one NDA circuit's loops, circuit accordingly devised. In order validate procedure, implemented 0.1-μm GaAs pHEMT process. predicted, measurements show oscillations, once on-chip disabled.