| 摘要 |
<p>PURPOSE:To obtain a high-speed operation and sufficient output voltage, by connecting the first transistor in series with a semiconductor light-receiving element and performing current mirror connection of the second transistor in parallel with the first transistor and drawing out an output from the second transistor. CONSTITUTION:When light hnu becomes incident to a photodiode 1, a current ld flows from a cathode side of the diode 1 to its anode side. Because of small internal resistance of the first transistor 3, the current Id receives almost no effect of diode 1's junction capacity 1a and diode 1's wiring capacity and flows to the earth GND through the transistor 3. For example, when 40 muA current flows across the transistor 3, a base potential of the first transistor 3 becomes 0.61 V and also the base potential of the second transistor 5 becomes 0.61 V, so that 40 muA current flows across the transistor 5 similarly with the transistor 3. Thus, a power voltage Vcc is lowered by a voltage applied between both terminals of a resistor 4, and the voltage obtained by this subtraction is outputted from an output terminal 6.</p> |
