Fig.3 Simulated spectrum.
Simulation results: This work is verified by SPICE simulations. A 10-bit second-order NS-SAR ADC with NTF of (1-0.75z-1)2 is designed. The simulated spectrum is shown in Fig. 3, it shows the second-order shaping noise slope. With the input signal frequency of 3.8 MHz and sampling rate of 200 MS/s, the SNDR is 83.2 dB in 20MHz bandwidth.
Conclusion: The work proposes a noise-shaping SAR ADC with 2× passive gain. Comparing to prior works, it can reduce the total capacitor size and comparator power consumption. It also obviates the capacitor stacking, leading to less signal attenuations. It has a simple circuit structure and is easy for high-order extension.
Acknowledgments: This work was supported by NSFC under Grant 62174023, Grant 62090041, and Grant 62090042.