A 5 GHz, 192.6 dBc/Hz/mW FOM, LC–VCO System With Amplitude Control Loop and LDO Voltage Regulator in 0.18 $\mu$m CMOS

To reduce phase noise degradation from oscillator tail current sources, this letter presents an inductor-capacitor voltage-controlled oscillator (LC-VCO) biased by triode metal-oxide-semiconductor transistors. The VCO system also includes an amplitude control loop and a voltage regulator to endure process, voltage, and temperature variations and to enhance power supply rejection ratio. Fabricated in a 0.18 mum CMOS process, the measured results show the adopted topology achieves a better phase noise than the conventional saturation current source. At 5.181 GHz, the VCO system demonstrates a phase noise of -104.8 dBc/Hz at 100-kHz offset, and -127.1 dBc/Hz at 1 MHz offset, while dissipating 4.2 mA from a 1.8 V supply voltage. The corresponding figures of merit at 100 kHz and 1 MHz offset are 190.3 and 192.6 dBc/Hz/mW, respectively.