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This paper discusses the design of 77-106 GHz Colpitts VCOs fabricated in two generations of SiGe BiCMOS technology, with MOS and HBT varactors, and with integrated inductors. Based on a study of the optimal biasing conditions for minimum phase noise, it is shown that VCOs can be used to monitor the mm-wave noise performance of SiGe HBTs. Measurements show a 106 GHz VCO operating from 2.5 V with phase noise of -101.3 dBc/Hz at 1 MHz offset, which delivers +2.5 dBm of differential output power at 25degC, with operation verified up to 125degC. A BiCMOS VCO with a differential MOS-HBT cascode output buffer using 130 nm MOSFETs delivers +10.5 dBm of output power at 87 GHz.