A vacuum tube for amplifier circuit includes: a light incidence window that transmits signal light; a photoelectric conversion unit that converts the signal light transmitted through the light incidence window into photoelectrons; an output unit that has an anode, on which the photoelectrons are incident, and outputs a signal corresponding to the incident photoelectrons; and a grid electrode that is disposed in a path of the photoelectrons from the photoelectric conversion unit to the anode and controls the amount of photoelectrons incident on the anode.

A vacuum tube for amplifier circuit includes: a light incidence window that transmits signal light; a photoelectric conversion unit that converts the signal light transmitted through the light incidence window into photoelectrons; an output unit that has an anode, on which the photoelectrons are incident, and outputs a signal corresponding to the incident photoelectrons; and a grid electrode that is disposed in a path of the photoelectrons from the photoelectric conversion unit to the anode and controls the amount of photoelectrons incident on the anode.

A power amplifier circuit includes a first amplifier circuit configured to amplify a first signal of a first frequency band and output a first amplified signal having a first power, a second amplifier circuit configured to amplify a second signal of the first frequency band or a second frequency band different from the first frequency band and output a second amplified signal having a second power different from the first power, and a first variable adjustment circuit disposed between the second amplifier circuit and a first circuit subsequent to the second amplifier circuit, the first variable adjustment circuit being configured to be capable of adjusting a first impedance of the first circuit seen from the second amplifier circuit.

A low power amplifier architecture that employs a single-ended (single triode) push-pull (SEPP) vacuum tube and output transformer arrangement, and that cancels unwanted amplifier signal components such as hum and noise. The SEPP amplifier operates to cancel power supply ripple and local EMI induced noise in the output transformer by providing reverse polarity of the primary coils of the output transformer.

A low power amplifier architecture that employs a single-ended (single triode) push-pull (SEPP) vacuum tube and output transformer arrangement, and that cancels unwanted amplifier signal components such as hum and noise. The SEPP amplifier operates to cancel power supply ripple and local EMI induced noise in the output transformer by providing reverse polarity of the primary coils of the output transformer.

Methods and devices for amplifying an input RF signal according to at least two gain-states is described. According to one aspect, a multi gain amplifier circuit including a low noise amplifier having a stack of transistors is used for amplification of the input RF signal. When switching from a low gain-state to a high gain-state, the drain-to-source voltage of the output transistor of the stack is increased to affect region of operation of the output transistor, and thereby reduce non-linearity at the output of the amplifier. When switching from the high gain-state to the low gain-state, the drain-to-source voltage of the input transistor of the stack is increased to affect region of operation of the input transistor, and thereby reduce non-linearity at the output of the amplifier.

Methods and devices for amplifying an input RF signal according to at least two gain-states is described. According to one aspect, a multi gain amplifier circuit including a low noise amplifier having a stack of transistors is used for amplification of the input RF signal. When switching from a low gain-state to a high gain-state, the drain-to-source voltage of the output transistor of the stack is increased to affect region of operation of the output transistor, and thereby reduce non-linearity at the output of the amplifier. When switching from the high gain-state to the low gain-state, the drain-to-source voltage of the input transistor of the stack is increased to affect region of operation of the input transistor, and thereby reduce non-linearity at the output of the amplifier.

An amplifying circuit includes a floating inverter amplifier and a voltage generating circuit. A threshold voltage of transistors in the floating inverter amplifier varies corresponding to an environmental condition. The voltage generating circuit is coupled with the floating inverter amplifier. The voltage generating circuit is configured to provide an operating voltage to the floating inverter amplifier. The operating voltage provided by the voltage generating circuit is linearly correlated to the threshold voltage, and the voltage generating circuit modulates a variation of the operating voltage to keep track with a variation of the threshold voltage.

An amplifying circuit includes a floating inverter amplifier and a voltage generating circuit. A threshold voltage of transistors in the floating inverter amplifier varies corresponding to an environmental condition. The voltage generating circuit is coupled with the floating inverter amplifier. The voltage generating circuit is configured to provide an operating voltage to the floating inverter amplifier. The operating voltage provided by the voltage generating circuit is linearly correlated to the threshold voltage, and the voltage generating circuit modulates a variation of the operating voltage to keep track with a variation of the threshold voltage.

Methods and devices for amplifying an input RF signal according to at least two gain-states is described. According to one aspect, a multi gain amplifier circuit including a low noise amplifier having a stack of transistors is used for amplification of the input RF signal. When switching from a low gain-state to a high gain-state, the drain-to-source voltage of the output transistor of the stack is increased to affect region of operation of the output transistor, and thereby reduce non-linearity at the output of the amplifier. When switching from the high gain-state to the low gain-state, the drain-to-source voltage of the input transistor of the stack is increased to affect region of operation of the input transistor, and thereby reduce non-linearity at the output of the amplifier.