Abstract: A relaxation oscillator, such as a voltage controlled oscillator (VCO), with automatic swing control feedback which dynamically monitors the voltage swing across a capacitor and adjusts the oscillator threshold voltage, at which reversal of the polarity of the charging/discharging current occurs, to maintain the effective voltage swing at a constant level. The improved relaxation oscillator provides a very wide linear range of frequency variation versus control voltage (or current) and allows for the extendibility of linear operation to or near the maximum frequency that can be practically achieved by the oscillator circuitry.