| 摘要 |
PURPOSE:To enable use for high-speed data transmission by a method wherein a differential amplifier is constructed in two stages: the collector side common connection point of the two transistors of the first stage differential amplifier is connected to the power source via resistor. CONSTITUTION:When the input is at high level, a diode 2 is turned OFF; at this time, since a comparison potential A is higher than a comparison potential B, a transistor 22 turns ON, and a transistor 23 turns OFF. If the current value I1 of a current source 27 is therefore kept higher than that of the base current when the next stage transistor 25 turns ON, the pontential E of a point 41 becomes higher than the potential D of a point 40, and so light is emitted by flows of current through a LED26. When the input in at low level, the photo diode 21 turns ON; then, the comparison potential A of a point 37 becomes lower than the comparison potential B of a point 38 because being VBE. Consequently, the transistor 22 turns OFF, and the transistor 23 turns ON. Therefore, if the current value I1 of the current source 27 is kept higher than that of the base current when the next stage transistor 24 turns ON, the potential E becomes lower than the potential D, and so current comes difficult to flow through the LED26, and light is extinguished. |
