| 摘要 |
<p>A tuning circuit which has a wide tuning bandwidth. The tuning bandwidth or the tuning frequency can be easily changed. The tuning circuit (1) is imposed of two cascade-connected tuning amplifier sections (2 and 3). Each of the sections (2 and 3) is provided with cascade-connected phase-shifting circuits (10C and 30C), a noninverting circuit (50), a voltage dividing circuit (160), and an aadding circuit composed of a feedback resistor (70) and an input resistor (74). Prescribed tuning operation is performed by shifting the prescribed frequency 360° by means of the phase shifting circuits (10C and 30C) and setting the open loop gain of a feedback loop at less than 1 when the output of the voltage dividing circuit (160) is feedback. The resistance ratio between the feedback resistor (70) and the input resistor (74) of each section (2, 3) is adjusted so that the maximum damping of each section (2, 3) may become smaller and the tuning bandwidth of each section (2, 3) becomes wider. Therefore, since the two tuning amplifier sections are cascade-connected, the maximum damping is increased and thetuning bandwidth is widened as a whole.</p> |
