A broadband amplifier from 75 to 140 GHz in SiGe 0.13-µm process is designed, fabricated, and measured. To control the base current effectively, the current mirrors are applied in the amplifier to feed the base current. The measured results of the gain and return losses agree with the simulation. It provides average gain of 11 dB from 75 to 140 GHz and gain-bandwidth product of 231 GHz. To the author's knowledge, this amplifier exhibits the highest percentage bandwidth for Si-based MMIC amplifiers around 100 GHz except distributed amplifiers.