The HMC391LP4 is a GaAs InGaP Heterojunction Bipolar Transistor (HBT) MMIC VCO with integrated resonator, negative resistance device, varactor diode, and buffer amplifier. Covering 3.9 to 4.45 GHz, the VCO's phase noise performance is excellent over temperature, shock, vibration and process due to the oscillator's monolithic structure. Power output is 5.0 dBm typical from a single supply of +3V @ 30 mA. The voltage controlled oscillator is packaged in a low cost leadless QFN 4 x 4 mm surface mount package.