This letter presents a mm-wave wideband amplifier implemented in a 130-nm SiGe BiCMOS technology operating up to 100 GHz. For the wideband operation, a new wideband technique based on low-impedance coupled line structure was proposed and adopted to the amplifier in combination with other bandwidth extension techniques. The enhancement of the amplifier bandwidth with the low-impedance coupled lines employed at the input and output matching networks is introduced in detail along with methodologies for actual implementation. The fabricated amplifier showed a peak gain of 13.2 dB with a 3-dB bandwidth of 90 GHz, covering from 10 to 100 GHz. The power consumption of the amplifier is 117 mW. The chip size is $865\times 344\,\,\mu \text{m}^{2}$ excluding probing pads.