| 摘要 |
PURPOSE:To prevent the fluctuation in a hold value and to widen the dynamic range of a phase difference detecting circuit, by shifting an output of the phase difference detecting circuit to a constant voltage source at the holding of a phase difference detecting value. CONSTITUTION:Two signals A, B for phase comparison are inputted to the phase difference detecting circuit 3 and the detected phase difference is detected as a voltage at a point (a). That is, switches 7, 8 are turned on at the detection of phase difference, a transistor 18 turns off, and a voltage at the point (a) is held in a capacitor 11 via a transistor(TR) 9 acting like an emitter follower. The switches 7, 8 are turned off at the holding of phase difference and the TR18 is turned on, then the voltage at the point (a) is increased to turn off completely the TR9, allowing to improve the holding characteristic. |
