Abstract: A Microwave reflection amplifier having improved gain, bandwidth and noise characteristics, uses two negative-resistance diodes, such as Gunn-effect diodes, connected in series across the terminals. The diodes are series resonated by inductance in their leads. The gain and bandwidth are higher than in amplifiers using a single diode. A shunt-resonant circuit is connected across one diode to improve the gain-bandwidth. A second shunt-resonant circuit may be connected across the terminals. At very high frequencies, the amplifier uses strip-line or microstrip circuitry and the shunt resonators are half-wavelength transmission lines.