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The sensitivity of an electrothermal displacement sensor is heavily dependent on its noise profile, particularly on the flicker noise inherent to the doped silicon heater. We show that the flicker noise in a microelectromechanical systems (MEMS) electrothermal displacement sensor can be reduced by driving the silicon heaters with a high-frequency voltage. The proposed technique has been applied to a MEMS electrothermal sensor fabricated in the standard silicon-on-insulator process. Experimental results demonstrate an 8-dB improvement in noise level compared to the conventional measurement technique. The achieved noise floor is less than -100 dBVrms around the 20-Hz measured signal.