A circuit for converting a lower voltage logical signal to a higher voltage. The circuit comprises a current mirror structure having first and second branches, each comprising at least a first transistor of a first kind, an input transistor of a second kind, and a second transistor of the first kind coupled between them. The first transistors are arranged as a current mirror. The input transistors are driven using a logical signal at the lower voltage, controlling the current mirror structure to output a corresponding logical signal at the higher voltage. The second transistors are driven by an intermediate reference voltage so as to reduce the operating voltage of the third transistors. The first kind is tolerant of a higher operating voltage than the second kind.