CMOS output buffer having a switchable bulk line

A CMOS output buffer circuit includes a final amplifier stage having a pull-up transistor and a pull-down transistor connected between a voltage supply and ground and having a common output node, and a control circuitry for driving the final amplifier stage including a first logic gate supplied with an input data signal, the first logic gate driving the pull-up transistor, a second logic gate supplied with said input data signal, the second logic gate driving the pull-down transistor. The pull-up transistor has a bulk electrode connected to a switchable bulk line; an auxiliary circuit is provided which as long as a voltage of the output node is not higher than said supply voltage keeps said switchable bulk line connected to the voltage supply. The first logic gate includes circuitry for transferring the voltage of the output node to said switchable bulk line when the voltage of the output node exceeds the supply voltage.