The equivalent electrical circuits - including the parasitic elements and their variations with the injected bias current - for three semiconductor optical amplifiers (SOA) were obtained. Frequency domain measurements with further tuning of numerical modeling parameters were used to extract circuit parameters. Characterization of chip-on-carrier and encapsulated devices agree with numerical data up to 20 GHz. The results are relevant for designing fast speed, SOA-gated switches in optical routers. (C) 2014 Elsevier B.V All rights reserved.