Patent ID: 8633618

Claim:
A semiconductor device, comprising: a negative bias generating circuit; and an antenna switch circuit of silicon on insulator, to be coupled to an antenna, and which has a plurality of switch transistors including a first switch transistor (Rx) and a second switch transistor (Tx), wherein a gate of at least one of the switch transistors which is in an off state receives a negative bias from the negative bias generating circuit, and wherein the negative bias generating circuit includes: an oscillation circuit that switches an output thereof between high frequency oscillation and low frequency oscillation; a down converter circuit that includes a first capacitor and stores charges in the first capacitor by an output of the oscillation circuit; a charge capacity switching circuit; and a second capacitor that is coupled in parallel to the first capacitor and electrically disconnectable by the charge capacity switching circuit, wherein the oscillation circuit performs high frequency oscillation when the semiconductor device is in an on state, wherein the charge capacity switching circuit electrically disconnects the second capacitor from the first capacitor, and wherein the down converter circuit stores charges in the first capacitor.