High-frequency amplifier circuitry and semiconductor device

A high-frequency amplifier circuitry, comprising:

• a first amplifier circuitry comprising a first transistor and a grounded-gate third transistor which are cascode-connected, the first transistor having a source grounded via a first source inductor and a gate to which an input signal is applied, the third transistor configured to output from a drain a signal obtained by amplifying a signal outputted from a drain of the first transistor;
• and
• a second amplifier circuitry having a same circuit constant as a circuit constant of the first amplifier circuitry and comprising a second transistor and a grounded-gate fourth transistor which are cascode-connected, the second transistor having a source grounded via a second source inductor and a gate to which the input signal is applied, the fourth transistor configured to output from a drain a signal obtained by amplifying a signal outputted from a drain of the second transistor;
• and
• an isolation improving circuitry connecting the drain of the third transistor and the drain of the fourth transistor to each other via a circuitry having a capacitor and a resistor connected in series, and
• having a single output mode of outputting the amplified signal from one of the first amplifier circuitry and the second amplifier circuitry, and a split output mode of outputting the amplified signal from both of the first amplifier circuitry and the second amplifier circuitry.

A semiconductor device, comprising:

• a plurality of high-frequency amplifier circuitries arranged on a silicon on insulator (SOI) substrate;
• and
• a high-frequency switch arranged on the SOI substrate corresponding to each of the plurality of high-frequency amplifier circuitries, and configured to select one of a plurality of high-frequency signals and supply the selected signal to a corresponding high-frequency amplifier circuitry,
• at least one of the plurality of high-frequency amplifier circuitries comprising:
• a first amplifier circuitry comprising a first transistor and a grounded-gate third transistor which are cascode-connected, the first transistor having a source grounded via a first source inductor and a gate to which an input signal is applied, the third transistor configured to output from a drain a signal obtained by amplifying a signal outputted from a drain of the first transistor;
• and
• a second amplifier circuitry having a same circuit constant as a circuit constant of the first amplifier circuitry and comprising a second transistor and a grounded-gate fourth transistor which are cascode-connected, the second transistor having a source grounded via a second source inductor and a gate to which the input signal is applied, the fourth transistor configured to output from a drain a signal obtained by amplifying a signal outputted from a drain of the second transistor;
• and
• a noise figure improving circuitry connecting the source of the first transistor and the source of the second transistor to each other, and
• having a single output mode of outputting the amplified signal from one of the first amplifier circuitry and the second amplifier circuitry, and a split output mode of outputting the amplified signal from both of the first amplifier circuitry and the second amplifier circuitry.