| 摘要 |
While a switch SW4 is connected to "a"-terminal side, offset of a differential output voltage "A-" of a D/A converter 500a (500b) is held in a comparator 400, and is reflected to a reference voltage. Thereafter, the switch SW4 is switched to a "b"-terminal side, and offset of a differential output voltage "A+" of the D/A converter 500a (500b) is measured by the comparator 400. An error signal is outputted to a counter 412 so as to count up the counter 412. Such an operation is repeatedly carried out in which the count value is added to 1.7 V and then the added count value is inputted into the D/A converter 500a (500b), and such a count value latched in a latch at timing when the error signal is inverted is defined as an offset correction value. <IMAGE> |
