| 摘要 |
PURPOSE:To form an A/D converter and a D/A converter operated with no adjustment by the user and with monolithic IC by writing an error correction amount to a programmable ROM from an IC pin. CONSTITUTION:A current source 21 and a current switch 24 for low order 5-bit, a current source 22 and a current switch 25 for middle order 5-bit, a current source 23 and a current switch 26 for a high order 6-bit, and a power supply 41 for a high-order bit and for adjustment are provided. Then a transistor (TR)52 is turned on always by biasing the TR with resistors 92, 93. When the switch 24 is closed, the current value is measured and then the switch 26 is closed and the current value is measured, the difference with n objective current ratio 1024 is 4i, where the former current value is (i) and the latter current value is 1020i. In flowing a large current from a P-ROM write terminal in this case, a TR42 is turned on, a TR43 is turned off, a current of 4i is added to an output of a current source 23 and the current value when the switch 26 is closed is equal to an objective value. |
