The　dependence　of　series　resistance,　ideality　factor,　junction　voltage,　and　capacitance　on　the　applied　voltage　or　current　of　laser　diodes　(LDs)　is　determined　by　examining　forward　AC　behavior　together　with　I-V　characteristics.　The　experimental　results,　for　the　first　time,　demonstrate　that　the　junction　voltage　saturation　occurs　after　the　junction　voltage,　series　resistance,　ideality　factor,　and　junction　capacitance　simultaneously　show　step　offsets　near　the　threshold.　A　negative　capacitance　effect　in　LDs　is　also　observed　under　larger　voltages　or　lower　frequencies.