Transformer-free ultrasonic generator (100) for generating ultrasound, preferably for a hand-held device (400) to fix a body on a substrate by ultrasonic welding, comprises: a power amplifier (102) for amplifying an electrical power supply signal (104); and a pulse generator (106) for generating a pulsed control signal for controlling pulsed power amplifier such that power amplifier generates a pulsed drive signal as an amplified electric signal supply for driving an ultrasonic transducer. The ultrasonic transducer generates ultrasound during providing drive signal to ultrasonic transducer. Independent claims are also included for: (1) a hand-held device, preferably transformer free handheld device, for fixing a body on a substrate by ultrasonic welding, comprising a fixing portion for temporary fastening of the body on the hand-held device during ultrasonic welding, an ultrasonic generator for generating ultrasound, and for charging the fixing portion secured to the body with the ultrasound and to seal the b
