The impedance source inverter family has become one of the most interesting alternatives for wind and photo-voltaic energies applications which require high conversion ratio. The main drawback of these inverters is related to the modulation signal which must be used to control the output current and voltage conversion ratio simultaneously. To deal with this problem several modulation techniques and control methods have been proposed for these inverters. However, disregarding the control method or modulation technique employed, this type of inverters exhibits fundamental restrictions in its operating conditions, particularly the relation between conversion ratio and output current. In this paper, a modified impedance source inverter, the quasi-Z-source inverter, is analyzed and its operating region in terms of voltage ratio and output current is obtained. This operating region can be used to include limitations in the control scheme. Results of the inverter working inside and in the boundaries of the operating region demonstrate the validity of the analysis.