| 摘要 |
PURPOSE:To realize low-voltage operation by using a DC voltage obtained by rectifying and smoothing a signal as a control signal for a noise reducing device. CONSTITUTION:When the output signal of an emitter follower A is large, diodes 15a and 15b are conductive and the rectified signal is made into a direct current through capacitors C8 and C9 before being supplied to a voltage-current converter 27. When the output signal of the emitter follower A is small to the contrary, the diode 15a is conductive and the diode 15b is non-conductive. The signal rectified by the diode 15a is smoothed similarly. Schottky diodes are used for those diodes 15a and 15b. The Schottky type diode has an about 0.3V forward voltage, so even when a power voltage is about 3V, control over an compressor and expander is possible to obtain an small-sized, handy Dolby system. |
