| 摘要 |
PURPOSE:To dispense with adjustment by a manual operation and the setting of an adjusting means, by driving the load of a light emitting element, etc., by the output signal of a D/A converter, and performing the offset adjustment of the D/A converter and that of a signal transmission line from the D/A converter to the load automatically by detecting the presence/absence of the output current of the load. CONSTITUTION:The output signal V5 of a voltage comparator 6 is varied to a level '0' or a level '1' according to the light emission or the stoppage of the light emission of a LED. A CPU12 in a control part 11 reads the output signal V5, and supplies a signal to convert a level to the level '0' when it is the level '1' to a second D/A converter 7. As a result, the output signal V6 of the converter 7 is supplied to the reference terminal of a first D/A converter 1, then, the gain control of the converter 1 is performed. Furthermore, the level of the output signal V3 of the second D/A converter 7 changes, then, the gain control of a third amplifier circuit 4 is performed. Thus, since the offset of not only the D/A converter 1 but the signal transmission line to a driving circuit 3 is adjusted automatically based on the presence/absence of the output current of the LED, it is possible to make manual adjustment and the adjusting means for the offset unnecessary.
|
