Power amplifier

1. A power amplifier comprising:

a semiconductor substrate;

preceding-stage amplifying device on the semiconductor substrate, amplifying an input signal;

a following-stage amplifying device on the semiconductor substrate, amplifying an output signal of the preceding-stage amplifying device;

a preceding-stage bias circuit supplying bias currents to an input terminal of the preceding-stage amplifying device;

a following-stage bias circuit supplying bias currents to an input terminal of the following-stage amplifying device; and

an inter-stage matching circuit connected between an output terminal of the preceding-stage amplifying device and the input terminal of the following-stage amplifying device, wherein

the preceding-stage amplifying device includes a first field effect transistor, which is an enhancement mode field effect transistor including a source, a gate, and a drain,

the following-stage amplifying device includes a heterojunction bipolar transistor,

the inter-stage matching circuit includes a capacitance which galvanically separates the output terminal of the preceding-stage amplifying device from the input terminal of the following-stage amplifying device, and

the preceding-stage bias circuit includes:

a second field effect transistor that is an enhancement mode field effect transistor, having a gate through which a reference voltage is input, a drain connected to a power supply, and a source,

a resistor, and

a third field effect transistor, which is an enhancement mode field effect transistor, having a source that is grounded, and a gate and a drain which are connected

to the source of the second field effect transistor via the resistor, and

to the gate of the first field effect transistor.

2. A power amplifier comprising:

a semiconductor substrate;

a preceding-stage amplifying device on the semiconductor substrate, amplifying an input signal;

a following-stage amplifying device on the semiconductor substrate, amplifying an output signal of the preceding-stage amplifying device;

a preceding-stage bias circuit supplying bias currents to an input terminal of the preceding-stage amplifying device;

a following-stage bias circuit supplying bias currents to an input terminal of the following-stage amplifying device; and

an inter-stage matching circuit connected between an output terminal of the preceding-stage amplifying device and the input terminal of the following-stage amplifying device, wherein

the preceding-stage amplifying device includes a first field effect transistor, which is an enhancement mode field effect transistor including a source, a gate, and a drain,

the following-stage amplifying device includes a heterojunction bipolar transistor,

the inter-stage matching circuit includes a capacitance which galvanically separates the output terminal of the preceding-stage amplifying device from the input terminal of the following-stage amplifying device,

the preceding-stage amplifying device includes a second field effect transistor, which is an enhancement mode field effect transistor, having a source, a gate, and a drain, the source being connected to the drain of the first field effect transistor, and

the preceding-stage bias circuit includes:

a third field effect transistor, which is an enhancement mode field effect transistor, having a gate through which a reference voltage is input, a drain connected to a power supply, and a source,

first and second resistors, and

a fourth field effect transistor, which is an enhancement mode field effect transistor, having a source that is grounded, and a gate and a drain which are connected to

the source of the third field effect transistor via the first resistor and the second resistor,

the gate of the second field effect transistor via the first resistor, and

the gate of the first field effect transistor.

3. A power amplifier comprising:

a semiconductor substrate;

a preceding-stage amplifying device on the semiconductor substrate, amplifying an input signal;

a following-stage amplifying device on the semiconductor substrate, amplifying an output signal of the preceding-stage amplifying device;

a preceding-stage bias circuit supplying bias currents to an input terminal of the preceding-stage amplifying device;

a following-stage bias circuit supplying bias currents to an input terminal of the following-stage amplifying device;

an inter-stage matching circuit connected between an output terminal of the preceding-stage amplifying device and the input terminal of the following-stage amplifying device, wherein

the preceding-stage amplifying device includes a first field effect transistor, which is a depletion mode field effect transistor including a source, a gate, and a drain,

the following-stage amplifying device includes a heterojunction bipolar transistor, and

the inter-stage matching circuit includes a capacitance which galvanically separates the output terminal of the preceding-stage amplifying device from the input terminal of the following-stage amplifying device;

a second field effect transistor, which is an enhancement mode field effect transistor, switching connection of the drain of the first field effect transistor to a power source in response to an enable signal, wherein

the preceding-stage bias circuit includes:

a negative voltage generating circuit generating a negative voltage,

a level control circuit converting the negative voltage to a desired level in response to a reference voltage and outputting the negative voltage, as converted, to the gate of the first field effect transistor, and

a third field effect transistor that is an enhancement mode field effect transistor, switching connection of the negative voltage generating circuit and the level control circuit to a power source in response to the enable signal.

4. A power amplifier comprising:

a semiconductor substrate;

a preceding-stage amplifying device on the semiconductor substrate, amplifying an input signal;

a following-stage amplifying device on the semiconductor substrate, amplifying an output signal of the preceding-stage amplifying device;

a preceding-stage bias circuit supplying bias currents to an input terminal of the preceding-stage amplifying device;

a following-stage bias circuit supplying bias currents to an input terminal of the following-stage amplifying device; and

an inter-stage matching circuit connected between an output terminal of the preceding-stage amplifying device and the input terminal of the following-stage amplifying device, wherein

the preceding-stage amplifying device includes a first field effect transistor, which is a depletion mode field effect transistor including a source, a gate, and a drain,

the following-stage amplifying device includes a heterojunction bipolar transistor,

the inter-stage matching circuit includes a capacitance which galvanically separates the output terminal of the preceding-stage amplifying device from the input terminal of the following-stage amplifying device,

the preceding-stage amplifying device further includes:

a second field effect transistor, which is a depletion mode field effect transistor, having a source connected to the drain of the first field effect transistor, and

a third field effect transistor, which is an enhancement mode field effect transistor, switching connection of the drain of the second field effect transistor to a power source in response to an enable signal; and

the preceding-stage bias circuit includes:

a negative voltage generating circuit generating a negative voltage,

a level control circuit converting the negative voltage to a desired level in response to a reference voltage and outputting the negative voltage, as converted, to the gate of the first field effect transistor and the gate of the second field effect transistor, and

a fourth field effect transistor, which is an enhancement mode field effect transistor, switching connection of the negative voltage generating circuit and the level control circuit to a power source in response to the enable signal.