A circuit, comprising: - a differential transconductance amplifier having a first input node, a second input node, an output node, the output node coupled to the second input node via a feedback line, - a supply node and a drive node configured to be coupled to the current path through a transistor with said transistor intermediate the supply node and the drive node, the supply node configured to be coupled to a power supply source, - a control node configured to be coupled to the control electrode of said transistor, the control node coupled to the output node of the differential transconductance amplifier, characterised by - a zener diode arrangement having cathode and anode terminals coupled to the supply node and the first input node of the differential transconductance amplifier, - a pull-up component (20, 20') arranged in parallel to the zener diode arrangement, and - an enable switch coupled to the first input node of the differential transconductance amplifier, the enable switch referred to ground and switchable between: - i) a conductive state, with the first input node of the differential transconductance amplifier coupled to the supply node via the reverse-biased zener diode arrangement, and the differential transconductance amplifier providing controlled current discharging of the control node coupled to the output node of the differential transconductance amplifier to make said transistor conductive, and - ii) a non-conductive state, with the first input node of the differential circuit stage pulled up to the supply node via the pull-up component (20, 20') and the differential transconductance amplifier providing controlled current charging of the control node coupled to the output node of the differential transconductance amplifier to make said transistor non-conductive. - a differential transconductance amplifier having a first input node, a second input node, an output node, the output node coupled to the second input node via a feedback line, - a supply node and a drive node configured to be coupled to the current path through a transistor with said transistor intermediate the supply node and the drive node, the supply node configured to be coupled to a power supply source, - a control node configured to be coupled to the control electrode of said transistor, the control node coupled to the output node of the differential transconductance amplifier, characterised by - a zener diode arrangement having cathode and anode terminals coupled to the supply node and the first input node of the differential transconductance amplifier, - a pull-up component (20, 20') arranged in parallel to the zener diode arrangement, and - an enable switch coupled to the first input node of the differential transconductance amplifier, the enable switch referred to ground and switchable between: - i) a conductive state, with the first input node of the differential transconductance amplifier coupled to the supply node via the reverse-biased zener diode arrangement, and the differential transconductance amplifier providing controlled current discharging of the control node coupled to the output node of the differential transconductance amplifier to make said transistor conductive, and - ii) a non-conductive state, with the first input node of the differential circuit stage pulled up to the supply node via the pull-up component (20, 20') and the differential transconductance amplifier providing controlled current charging of the control node coupled to the output node of the differential transconductance amplifier to make said transistor non-conductive. - i) a conductive state, with the first input node of the differential transconductance amplifier coupled to the supply node via the reverse-biased zener diode arrangement, and the differential transconductance amplifier providing controlled current discharging of the control node coupled to the output node of the differential transconductance amplifier to make said transistor conductive, and - ii) a non-conductive state, with the first input node of the differential circuit stage pulled up to the supply node via the pull-up component (20, 20') and the differential transconductance amplifier providing controlled current charging of the control node coupled to the output node of the differential transconductance amplifier to make said transistor non-conductive.