| 摘要 |
PURPOSE:To decrease the cost and the A/D conversion time by using an inexpensive and low resolution A/D converter so as to realize the A/D conversion with high resolution with respect to the vicinity of a required voltage. CONSTITUTION:The titled converter consists of an A/D converter 1, a 1st amplifier circuit section 2, a 2nd amplifier circuit section 3, a selection circuit section 4 and a discrimination circuit section 5. Through the constitution above, the circuit section 2 amplifies an analog input signal up to an input level of the converter 1 as it is, while the circuit section 3 amplifies a differential voltage of an analog input signal up to an input level of the converter 1. The circuit section 4 has a switch 9 including two switch terminals S, T, and any of the 1st and 2nd amplifier circuits 2, 3 is connected to the converter 1 by the switching operation. The circuit section 5 obtains a converting value D2 from a digital output D1 of the converter 1 and amplification factors K1, K2, compares the value with a voltage range stored in advance to judge the level of the analog signal input. Then the section 5 gives a switching command to the circuit 4 to change over the switch 9 based on the result of judgement.
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