In this paper, a voltage-controlled oscillator (VCO) operating at H-band (220-330 GHz) with 250-nm InP HBT technologies is presented. The VCO is designed with a Colpitts topology to oscillate at a fundamental frequency of 250 GHz. A common-base output buffer amplifier is implemented to isolate the oscillator core from the output load, thereby reducing the load-pulling effect. The VCO is designed by using Agilent Advanced Design System (ADS) tools. Small and large signal analysis were implemented by ADS. The measured frequency tuning range of the VCO is 12.6 GHz, spanning from 226.2-238.8 GHz. The maximum output power was measured at 230 GHz and recorded as 2.7 dBm. The dc power consumption is 32.2 mW, resulting in a dc-to-RF conversion efficiency of 5.2 %. The measured phase noise is -71.2 dBc/Hz at 10-MHz offset frequency.