Abstract: A broadband, traveling wave amplifier which includes a target anode and an lectron gun for bombarding the anode with an electron beam having an amplitude proportional to that of an input signal. The electron gun includes a NEA semiconductor cold cathode having an electron emitting surface and a modulation structure for modulating the emitted electron beam with an input signal to be amplified. The electron gun and the anode are configured as parallel strip transmission lines having the same phase velocity. The target anode may be a reversed-biased stripline diode, Schottky barrier stripline diode, or metal/semiconductor/metal stripline structure.