Single-ended to differential converter for multiple-stage single-ended ring oscillators

This paper presents an improved technique for single-ended to differential conversion that allows for the use of single-ended CMOS ring oscillators in an otherwise fully differential integrated circuit environment. An interpolating resistor network is used to derive a fully differential representation of the single-ended voltage-controlled-oscillator (VCO) signal. The technique preserves the fundamental noise performance of single-ended ring oscillators in the presence of supply and substrate interference. Experimental results in a 0.35-μm CMOS process show the applicability of this technique at the VCO speeds of up to 1.3 GHz.