Linearization of Voltage-Controlled Oscillators Using Floating-Gate Transistors

This brief presents a linearization method for the voltage-to-current (V-to-I) stage of voltage-controlled oscillators (VCOs). A floating-gate transistor is utilized at the VCO's input stage as a low-overhead method for V-to-I linearization. The resulting VCO is a ring oscillator with an extended linear voltage-to-frequency range. The ring oscillator VCO (RO-VCO) has also been included in a VCO-based analog-to-digital converter (VCO-ADC) to showcase how the linearization technique can be leveraged to improve system performance. The measured results from the linearized RO-VCO are compared to current state-of-the-art designs, and the VCO-ADC is compared to a standard architecture. The circuits were fabricated in a standard 0.35 μm complementary metal-oxide-semiconductor (CMOS) process.