A driving circuit has output terminal connected to an ultrasonic transducer and provides an output voltage. The driving circuit includes an output transistor coupled between a voltage reference and the output terminal, a high voltage comparator coupled to said output terminal and to a threshold voltage reference), a start-up circuit controlled by a setting signal; and a switching ON/OFF circuit having an input coupled to the start-up circuit an input coupled to the comparator, and an output coupled to a control terminal of the output transistor. The start-up circuit provides an ON signal to the switching on/off circuit and the comparator provides an OFF signal to the switching on/off circuit which switches off the output transistor. The high voltage comparator generates the switching off signal in response to the output voltage reaching a desired supply voltage value which depends on the value of the first threshold voltage reference.