A pressurized air supply unit (1; 1′) for an aircraft, comprising: a load compressor (30; 30′) configured to supply pressurized air (3), the load compressor (30; 30′) having a compressor shaft (23; 23′); and a drive portion (10) configured to supply power via an output shaft (20); the pressurized air supply unit (1; 1) being characterized in that it comprises: a gearbox (50); an electric motor (40), the electric motor (40) being coupled to said compressor shaft (23; 23′) via the gearbox (50); and a coupling system (25) configured to enable the output shaft (20) to drive the compressor shaft (23; 23′) and to prevent the compressor shaft (23; 23′) from driving the output shaft (20), and in that the output shaft (20) and the compressor shaft (23) lie on the same axis.