a ferroresonant ballast for regulating the current level of gas discharge lamps includes a magnetic core for supporting coil windings . a first or input coil is wound about the magnetic core for supplying a changing input voltage . a second or capacitor coil is wound about the magnetic core and is induced by the first coil to generate an output voltage across an output or resonant capacitor . a third or lamp coil is wound about the magnetic core and coupled to a gas discharge lamp which is regulated at a constant voltage in response to the voltage generated across the output capacitor . the ferroresonant ballast may include a control circuit and inductor that is switchable coupled to the output capacitor for simulating core saturation .