A microdevice has an electron emitter including a memory for accumulating electric charges corresponding to an input voltage, for emitting electrons corresponding to the electric charges accumulated in said memory; and an amplifier connected to a power supply and including a collector electrode for capturing the electrons emitted from the electron emitter. The atmosphere between at least the electron emitter and the collector electrode is a vacuum. When the electrons emitted from the electron emitter are captured by the collector electrode of the amplifier, a collector current flows between the collector electrode and the electron emitter to amplify the input voltage.