| CPC H03F 3/02 (2013.01) [H01J 19/02 (2013.01); H01J 19/54 (2013.01)] | 19 Claims |

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1. A vacuum tube for amplifier circuit, the amplifier circuit configured to receive a signal input to generate an amplification signal, the vacuum tube comprising:
an incidence window portion configured to transmit signal light;
a photoelectric conversion unit configured to convert the signal light transmitted through the incidence window portion into photoelectrons;
an output unit configured to have an anode, on which the photoelectrons are incident, and output a signal associated with the amplification signal, and the signal corresponding to the photoelectrons incident on the anode; and
a grid electrode configured to be disposed in a path of the photoelectrons from the photoelectric conversion unit to the anode and control an amount of the photoelectrons incident on the anode based on the signal input.
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