Abstract: In this paper working principle and its application of self-tuned filter has been described and its configuration given with two particular design improvements: a symmetrical nonlinear feedback loop is provided with the Junction FET and an ideal hard-limiter incorporated. There-fore the basic Characteristic of the self-tuned filter is improved completely. A brief analysis of the self-tuned filter has been made. It has demonstrated that system perfor-mances are substantially enharced with the use of self-tuned filter.