Patent ID: 7391282

Claim:
A radio-frequency switch circuit for controlling flow of a radio-frequency signal, comprising: a plurality of field-effect transistors inserted between an input/output terminal and a ground terminal and connected in series, a radio-frequency signal being input and output through the input/output terminal; and a plurality of resistance elements, wherein each of the plurality of resistance elements has two terminals, one of the two terminals is connected to a gate electrode of a corresponding one of the plurality of field-effect transistors, and a control voltage for switching an ON state and an OFF state of the corresponding field-effect transistor is applied to the other of the two terminals, wherein one of the plurality of resistance elements connected to a gate electrode of one of the plurality of field-effect transistors connected to the input/output terminal has a highest resistance value among the plurality of resistance elements, and wherein: first to n-th (n is an integer of 2 or more) field-effect transistors are connected in series and in order of first to n-th between from the input/output terminal to the ground terminal; and resistance values Rgs( 1 ) to Rgs(n) of first to n-th resistance elements connected to gate electrodes of the first to n-th field-effect transistors are set based on the following expression: Rgs (1)> Rgs (2)≧ . . . ≧Rgs ( n− 1)≧ Rgs ( n ).