PURPOSE: To make a chip area small, to reduce cost and to improve yield by using a plural switches so as to switch over plural voltage levels and inputting the voltage level to a voltage amplifier of a high input impedance and receiving a signal passing through the switch at a high input impedance.
CONSTITUTION: The attenuator is made of a fixed attenuation generating section 4 formed by connecting resistors 4-1-4-n in series, a fixed attenuation selection section 5 comprising n-set of FET switches 5-1-5-n, an amplifier section 6 connecting to an output of the fixed attenuation selection section 5 in which the FET switches are connected in common and amplifying the voltage output and a control signal generating section 3 connecting to control terminals of the n-set of FET switches of the fixed attenuation selection section 5 and applying a control signal to close only one of the FET switches. Then plural voltage levels obtained by dividing a voltage converted from input power are switched by the plural switches 4-1 to 4-n and the selected voltage is received by a voltage amplifier 6 with a high input impedance.
HIGUCHI MASAHIRO