| 摘要 |
PURPOSE:To obtain a program shutter with high response efficiency by connecting a diode between the emitter of an output transistor and an earth, applying a logarithmic compressing value to its base and obtaining out current in proportion to the square root of photocurrent from its collector. CONSTITUTION:Constant current Ir from a constant current source 1 is supplied to a transistor 2 connected with a diode and the output voltage of the 1st operation amplifier 3 is expressed by V3=(KT/q)lnIr/IO. If optical current generated in a photodetector 5 is IL, the output voltage of the 2nd operational amplifier 6 is expressed by V6=(KT/q)(lnIr/IO+lnIL/IO). Since the collector current Ic (=output current Iout) of an output transistor 7 is equal to the current flowing into a transistor 8, the base voltage of the transistor 7 is V7=2X(KT/q)/lnIout/ IO. From V7=V6, IrIL=I<2> out is obtained. |
