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设计了一个用于12位40 MS/s流水线A/D转换器的MDAC电路。为了实现这一较高精度,对传统1.5位/级电路的传输特性进行改进。在改进后电路的传输特性中,当输入信号摆幅加倍时,输出信号摆幅与传统结构相比保持不变,这样既提高了电路信噪比,又不增加运放设计的难度。另外,还设计了实现改进传输特性的电路结构。该MDAC采用TSMC 0.35μm 3.3 V工艺设计,以奈奎斯特频率采样时,仿真结果显示,电路的输入摆幅可达到输出摆幅的两倍,SINAD为73.4 dB,ENOB为11.9位,SFDR为89.0 dB。与传统结构相比,ENOB和SFDR分别提高0.7位和7.7 dB。
An MDAC circuit was designed for a 12-bit 40 MS / s pipelined A / D converter. In order to achieve this higher accuracy, the transmission characteristics of the conventional 1.5-bit / stage circuit are improved. In the improved transmission characteristics of the circuit, when the input signal amplitude doubled, the output signal swing compared with the traditional structure remains unchanged, so that not only improve the circuit SNR, without increasing the difficulty of op amp design. In addition, a circuit structure that realizes improved transmission characteristics is also designed. The MDAC is designed with the TSMC 0.35μm 3.3 V process. When sampling at Nyquist frequency, the simulation results show that the input swing of the circuit can reach twice the output swing, the SINAD is 73.4 dB, and the ENOB is 11.9 bits. The SFDR is 89.0 dB. Compared with the traditional structure, ENOB and SFDR increased by 0.7 and 7.7 dB respectively.