Amplifier

An amplifier having a gain extension characteristic which presents an increase in gain in response to an increase in input power or output power in a certain range of the input power or the output power, said amplifier characterized in that:

• a mechanism for compressing an amplitude at high frequencies is provided at an input of said amplifier.

An amplifier having a gain extension characteristic which presents an increase in gain in response to an increase in input power or output power in a certain range of the input power or the output power, said amplifier characterized in that:

• an emitter grounded amplifier circuit comprising a first bipolar transistor has a base terminal to which an input matching circuit and a cathode of a first diode for supplying a bias voltage are connected through a first impedance element which does not block a direct current, and said first diode has an anode which is connected to a reference power supply which presents a sufficiently low impedance at high frequencies.

An amplifier having a gain extension characteristic which presents an increase in gain in response to an increase in input power or output power in a certain range of the input power or the output power, said amplifier characterized in that:

• a first diode is arranged in a forward direction between a base terminal of an emitter grounded amplifier circuit comprising a first bipolar transistor and a reference voltage terminal for supplying a base bias voltage to the base terminal, and a circuit comprising a second diode connected in series with a first impedance element which does not block a direct current is connected in parallel with said first diode such that said second diode is oriented in the forward direction.

7-20. (canceled)

A multi-stage amplifier comprising at least two or more amplification stages and having a gain extension characteristic which presents an increase in gain in response to an increase in input power or output power in a certain range of the input power or the output power, said multi-stage amplifier characterized in that:

• in a power range in which the gain extension characteristic is provided, at least one stage of said amplification stages other than a final stage has an output characteristic such that when said amplifier is applied with two wave signals at close frequencies, a phase of a third-order inter-modulation distortion rotates 90 degrees or more from the phase of the two wave signals at a time when the two wave signals match in phase.

A multi-stage amplifier comprising at least two or more amplification stages which have a gain extension characteristic which presents an increase in gain in response to an increase in input power or output power in a certain range of the input power or the output power, said multi-stage amplifier characterized in that:

• a mechanism for compressing an amplitude at high frequencies is provided at an input of at least one stage of said amplification stages other than a final stage.

A multi-stage amplifier comprising at least two or more amplification stages which have a gain extension characteristic which presents an increase in gain in response to an increase in input power or output power in a certain range of the input power or the output power, said multi-stage amplifier characterized in that:

• an amplifier of at least one stage of said amplification stages other than a final stage comprises an emitter grounded amplifier circuit including a first bipolar transistor which has a base terminal connected to an input matching circuit and to a cathode of a first diode for supplying a bias, wherein said first diode has an anode connected to a reference power supply which presents a sufficiently low impedance at high frequencies.

A multi-stage amplifier comprising at least two or more amplification stages which have a gain extension characteristic which presents an increase in gain in response to an increase in input power or output power in a certain range of the input power or the output power, said multi-stage amplifier characterized in that:

• an amplifier of at least one stage of said amplification stages other than a final stage comprises a first diode arranged in a forward direction between a base terminal of an emitter grounded amplifier circuit comprising a first bipolar transistor and a reference voltage terminal for supplying a base bias voltage to the base terminal, and a circuit having a second diode connected in series with a first impedance element, connected in parallel with said first diode such that said second diode is oriented in the forward direction.