Patent ID: 8217817

Claim:
A current switch circuit comprising a current source and a differential switch connected to an output terminal of the current source, wherein the current source includes at least one transistor having a gate terminal to which a bias voltage is applied that determines a value of a current to conduct, the differential switch includes first and second transistors, the transistors having source terminals connected to an output terminal of the current source in parallel, drain terminals as first and second output terminals respectively, and gate terminals to which complementary signals are inputted, the first and second transistors of the differential switch has the threshold voltage determined to have an absolute value greater than an absolute value of a threshold voltage of the transistor included in the current source, the transistor included in the current source is formed of a low voltage withstanding transistor having a gate insulating film with a predetermined thickness, each of the first and second transistors included in the differential switch is formed of a high voltage withstanding transistors having a gate insulating film with a thickness thicker than the predetermined thickness of the gate insulating film of the low voltage withstanding transistor, and the threshold voltage of the first and second transistors included in the differential switch is determined higher than a threshold voltage of the transistor included in the current source.