Variable attenuator

A switching element with variable attenuation comprising:

• a first SPST switch comprising a first inductive element connected to one of the source and the drain of a first FET thereby forming a first series connection of the first inductive element and the first FET, a first capacitive element connected in parallel with the first series connection of the first inductive element and the first FET, a first terminal and a second terminal respectively connected to both ends of the first capacitive element, and an attenuation setting unit which variably sets an amount of attenuation to a signal flowing between the first terminal and the second terminal by varying a voltage difference between the gate of the first FET and one of the source and drain;
• a second SPST switch comprising a second inductive element connected to one of the source and the drain of a second FET thereby forming a second series connection of the second inductive element and the second FET, a second capacitive element connected in parallel with the second series connection of the second inductive element and the second FET, a third terminal and a fourth terminal respectively connected to both ends of the second capacitive element, the third terminal being connected to the second terminal;
• and
• a voltage generator coupled to the gate of the second FET, and supplying a selected one of two constant voltage levels to the gate of the second FET, whereby said attenuation setting unit controls the conductive state of the first SPST switch and the voltage generator controls the conductive state of the second SPST switch.

A switching element with variable attenuation comprising:

• a first SPST switch comprising a first inductive element connected to one of the source and the drain of a first FET thereby forming a first series connection of the first inductive element and the first FET, a first capacitive element connected in parallel with the first series connection of the first inductive element and the first FET, a first terminal and a second terminal respectively connected to both ends of the first capacitive element, and an attenuation setting unit which variably sets an amount of attenuation to a signal flowing between the first terminal and the second terminal by varying a voltage difference between the gate of the first FET and one of the source and drain;
• and
• a second FET having one of its drains and source coupled to one of the drain and source of the first FET, a potential difference between the gate of the second FET and its drain or source being determined by said attenuation setting unit, the attenuation setting unit controlling the conductive state of the first SPST switch and the second FET,
• wherein the gates of said first and second FETs are coupled to a constant potential source and said attenuation setting unit is a variable voltage generator coupled to a common connection comprising at least one of a source and drain of each of the first and second FETs.

A switching element with variable attenuation comprising:

• a first SPST switch comprising a first inductive element connected to one of the source and the drain of a first FET thereby forming a first series connection of the first inductive element and the first FET, a first capacitive element connected in parallel with the first series connection of the first inductive element and the first FET, a first terminal and a second terminal respectively connected to both ends of the first capacitive element, and an attenuation setting unit which variably sets an amount of attenuation to a signal flowing between the first terminal and the second terminal by varying a voltage difference between the gate of the fist FET and one of the source and drain;
• and
• a second FET having one of its drains and source coupled to one of the drain and source of the first FET, a potential difference between the gate of the second FET and its drain or source being determined by said attenuation setting unit, the attenuation setting unit controlling the conductive state of the first SPST switch and the second FET,
• wherein said switching element has three terminals, a first terminal comprising a common connection comprising at least one of a source and drain of each of the first and second FETS, a second terminal comprising a common connection of said first capacitive element and said first inductive element and a third terminal comprising one of the source and drain of the second FET not connected to the common connection of said two FETS, and
• wherein one of said second and third terminals is connected to a constant potential source.