We present on-wafer and packaged measurements of a broad-band 170–280 GHz low noise amplifier based on high frequency InP HEMT technology. Discussed is the design and packaging of the CPW-based MMIC. Chip-to-waveguide transitions are monolithically integrated onto the MMIC to minimize losses at the transition within the split-block-waveguide housing. Packaged gain and noise figure are reported to be >10 dB, and < 7 dB, respectively, across the entire band of operation. Noise figure is < 6 dB on the 190–240 GHz band, with minimum noise figure reported to be 5.3 dB at 200 GHz.