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Two electronic ballasts have been built to drive lamps with sinusoidal and quasi-square-wave currents, respectively, in order to investigate the high-frequency operating characteristics of small-wattage metal-halide lamps. Experiments were conducted on the tested lamps of 35, 70, and 150 W with a frequency ranging from 20 to 300 kHz. The measurements include the spectral energy, the color temperature, the acoustic resonance, and the luminous efficiency. The effects of operating frequency are discussed based on the experimental results.