A step-up/step-down circuit can be simplified as compared with
conventional circuits by including a step-down unit for receiving a
system clock pulse alternately providing a reference voltage (GND) and a
system voltage V.sub.DD in a repeated manner to output a voltage V.sub.4
lower than the reference voltage (GND) by using a potential difference
between the reference voltage (GND) and the system voltage V.sub.DD, a
level shift unit for receiving the system clock pulse and the voltage
V.sub.4 output from the step-down unit to output a pulse signal V.sub.o
having a greater potential difference than the potential difference
between the reference voltage (GND) and the system voltage VDD, and a
step-up unit for receiving the pulse signal V.sub.o output from the level
shift unit to output a voltage V.sub.7 higher than the reference voltage
(GND).