Patent ID: 8847665

Claim:
A semiconductor device, comprising: an analog switch including a P channel transistor and an N channel transistor connected in parallel between an input terminal and an output terminal; and a variable voltage circuit configured to variably generates, according to an input voltage applied to the input terminal, potentials of a first gate voltage and first back gate voltage of the P channel transistor and of a second gate voltage and second back gate voltage of the N channel transistor, wherein the P channel transistor has a first gate withstanding voltage, and the N channel transistor has a second gate withstanding voltage wherein the input voltage has a potential in a range from a minimum voltage to a maximum voltage, wherein, for the P channel transistor, the variable voltage circuit sets the first back gate voltage to a voltage higher by a fourth voltage than the minimum voltage when the input voltage is in a first voltage range of voltages equal to or higher than the minimum voltage and equal to or lower than a first voltage which is higher by a third voltage than the minimum voltage, the variable voltage circuit sets the first back gate voltage to a voltage equal to or higher than the input voltage when the input voltage is in a second voltage range of voltages equal to or higher than the first voltage and equal to or lower than the maximum voltage, and the variable voltage circuit sets the first gate voltage to a voltage lower by the fourth voltage than the first back gate voltage when the input voltage is in the first or second voltage range, wherein, for the N channel transistor, the variable voltage circuit sets the second back gate voltage to a voltage lower by a sixth voltage than the maximum voltage when the input voltage is in a third voltage range of voltages equal to or lower than the maximum voltage and equal to or higher than a second voltage which is lower by a fifth voltage than the maximum voltage, the variable voltage circuit sets the second back gate voltage to the input voltage or lower when the input voltage is in a fourth voltage range of voltages equal to or lower than the second voltage and equal to or higher than the minimum voltage, and the variable voltage circuit sets the second gate voltage to a voltage higher by the sixth voltage than the second back gate voltage when the input voltage is in the third or fourth voltage range, and wherein the third and fourth voltages are equal to or lower than the first gate withstanding voltage, and the fifth and sixth voltages are equal to or lower than the second gate withstanding voltage.