| 摘要 |
PURPOSE:To obtain an inexpensive variable AD converter having a wide dynamic range, by using only a multiplying AD converter, an amplifier, a sample hold circuit and a comparator. CONSTITUTION:A switch 32 is selected to the position S1, an output of a multiplying AD converter MDAC3 is given to the amplifier 2, and an analog multiplexer MPX31 selects an input signal Ex1, then a variable gain amplifier 1 outputs an amplified signal E1. In this case, digital codes given from a muP5 to the MDAC3 are D0, D1, D2,...Dm. The muP5 turns off a switch 34 to get a smaple hold circuit 33 to hold to voltage E1 and to change over the switch 32 to the position S2. Then the MPX31 is made to select a reference voltage Es and the AD conversion is carried out with a loop of the comparator 37, the muP5 and the MDAC3. In this case, the gain is changed by changing the D0, D1,...Dm, allowing to perform the AD conversion with a wide dynamic range. |
