A 103.9-dB SNDR 5-kHz BW Continuous-Time Dynamic Zoom ADC with Switched Resistor Technique for Reducing Thermal Noise

In this paper, we present a 36 μW continuous-time Zoom (CT-Zoom) ADC with the switched resistor (SR) technique to reduce both the noise and area. The proposed CT-Zoom ADC effectively reduces in-band flicker noise using a chopped negative-R, and then further reduces in-band thermal noise by half through the use of the SR technique. This method halves the resistor in the first integrator, effectively solving the problem of thermal noise in CT-Zoom ADCs with a low-frequency signal bandwidth. The proposed dynamic CT-Zoom ADC exhibits post-layout simulation results with a peak signal-to-noise ratio (SNR) of 108.0 dB, a peak signal-to-noise and distortion ratio (SNDR) of 103.9 dB, and a total power consumption of 36 μW using a 1 V power supply, at a sampling frequency of 1.28 MHz for a 5-kHz signal bandwidth. The circuit was designed and simulated using the 28-nm CMOS process.