变形双极性逐位比较式模数转换器

逐位比较式模数转换器具有转换速度快、精度高、动态范围大等优点，因此在数字地震仪中得以广泛应用。DFS-V 数字地震仪采用了变形双极性模数转换器，其主要电路有:①二进制变形 T 网络，它提供的一套标准电压码，高四位是双极性，低十一位是单极性的;②两个比较器，第一比较器和二采保持电路对被转换子样信号放大-0.586倍后，再与二进制变形 T 网输出的标准电压码逐位比较，由第二比较器形成位舍电平 BRL;③模数转换器标准电压源;④模数转换器的逻辑控制电路。本文最后还就模数转换器的转换精度和调校问题进行了讨论。

Deformed dual-polarity bit-by-hit campare type analog-to-digital converter

Bit-by-bit compare type analog-to-digital converter is widely used in digital seismograph because of its merits such as higher converting speed, higher accuracy, wider dynamic range, etc. DFS-V seismic system uses deformed dual polarity analog-to-digital converter, which consists of the following major circuitss 1. Binary deformed T network, which provides a series of standard voltage codes whose four higher dual-polarity bits are followed by eleven lower single-polarity bits. 2. Two comparators after the first comparator and the second sample-and-hold circuit amplify the converted sample signal by a ratio -0.586, the amplified sample is bit by bit compared with the standard voltage codes which are output by binary deformed T network. The bit rejection level (BRL) is formed by the second comparator. 3. Reference voltage source. 4. Logic control cixcuit. Converting accuracy and calibration of analog-to-digital converter are also discussed.