TUNING CIRCUIT HAVING AMPLITUDE-VARYING FUNCTION AND IC FOR WIRELESS COMMUNICATION DEVICE

摘要

PURPOSE: A Tuning circuit having an amplitude-varying function and an IC for wireless communication device is provided to improve sensibility of the tuning circuit and detect an output signal by varying the tuning circuit to vary an amplitude of an output of the tuning circuit. CONSTITUTION: A tuning circuit having an amplitude-varying function includes a coil, a capacitor, and a resistance-adjusting element. The resistance-adjusting element is connected in parallel to the coil and the capacitor for varying resistance at time of resonance of the tuning circuit. An amplitude of an output signal of the tuning circuit is varied by varying the resistance with the resistance-adjusting element. The resistance-adjusting element includes a transistor. The resistance-adjusting element varies a voltage applied to a control electrode of the transistor in order to vary the resistance.