A level shifting circuit comprises a first low power, low speed level
shifter 30 and a second high power, high speed level shifter stage 31.
Both the stages 30, 31 have signal inputs connected to a common input IN
for receiving signals, at least one of whose levels is to be shifted. The
output of the first stage 30 is connected to an enable input EN2 of the
second stage 31 and switches the operation of the second stage 31 between
an enabled state and a disabled state in which the second stage 31
consumes little or no power. The first stage 30 has an enable input EN1
which may be permanently enabled.
