The tuning range is an important performance parameter of voltage-controlled oscillators (VCO), but as the tuning range increases, the oscillator amplitude will vary at different frequencies. This paper presents a circuit for automatic amplitude control that ensures that the oscillators amplitude remains constant. The automatic amplitude control uses a peak detector, a comparator and a low pass filter. The automatic amplitude control is connected to the VCO by a feedback loop to keep the VCO output constant. The circuits were fabricated using a standard 0.35μm complementary metal oxide semiconductor (CMOS) process. The measured VCO tuning range was from 18.2MHz to 24.3MHz, for a range of 28.7% while the automatic amplitude control circuit ensures that the VCO amplitude only varies by 8.7%.