A 160-310 GHz frequency doubler for rotational spectroscopy with a driver amplifier is demonstrated in a 65-nm bulk CMOS process. At 0-dBm input power, the measured output power (Pout) varies from 3 to -8 dBm. The wide operating range is attributed to wide bandwidth driver and matching structure based on broadband open and short leading to >40dB difference between fundamental and second harmonic power at the output. The doubler-amplifier combination has the comparable output power and a larger operating frequency range than 200-300 GHz COTS GaAs modules.