| 摘要 |
PURPOSE:To generate the stabilized titled noise of good quality by using inexpensive components, by a method wherein shot noise generating at the time of photoelectrically converting the light received from an LED by means of a photo diode is utilized as the noise source. CONSTITUTION:When a DC current I0 is flowed from an LED drive circuit 1 to the LED2a of a photo coupler 2, the noise is expressed by P0=alphaI0. This noise is amplified by an amplification circuit 4 to a necessary level and outputted to an output terminal 8; however, this unchanged state produces the possibility of variation in output noise level. Then, the effective value of the noise level outputted from the circuit 4 is detected by a detection circuit 5, and a current control circuit 6 controls the LED drive circuit 1 on the basis of the detection result of noise level, thereby changing the DC current I0 in the direction where the variation in noise level is cancelled. In other words, since the spectrum density P0 of output noise power and the current I0 flowing through the LED2a are in the relation of proportion, the current I0 can be increased in case of reduction in noise level and reversely decreased by the amount increment in case of increase in noise level. |
