This paper describes a fourth-order cascade-of-integrators with feedforward (CIFF) single-bit discrete-time (DT) switched-capacitor (SC) delta-sigma modulator (DSM) for high-resolution applications. This DSM is suitable for high-resolution applications at low frequency using a high-order modulator structure. The proposed operational transconductance amplifier (OTA), used a feedforward amplifier scheme that provided a high-power efficiency, a wider bandwidth, and a higher DC gain compared to recent designs. A chopper-stabilization technique was applied to the first integrator to remove the 1/f noise from the transistor, which is inversely proportional to the frequency. The designed DSM was implemented using 0.35 µm complementary metal oxide semiconductor (CMOS) technology. The oversampling ratio (OSR) was 128, and the sampling frequency was 128 kHz. At a 500 Hz bandwidth, the signal-to-noise ratio (SNR) was 100.3 dB, the signal-to-noise distortion ratio (SNDR) was 98.5 dB, and the dynamic range (DR) was 103 dB. The measured total power dissipation was 99 µW from a 3.3 V supply voltage.
A 20-MHz bandwidth, 75-dB dynamic range, continuoustime delta-sigma modulator with reduced nonidealities Summary This letter presents a 4-bit continuous-time delta-sigma modulator (CT-DSM) fabricated using a 65-nm CMOS process. The circuit is designed for wide-bandwidth applications, such as those related to wireless communications. This CT-DSM has an oversampling ratio of 16 with a 640-MHz sampling frequency. To reduce the clock jitter sensitivity and excess loop delay effect, the first DAC pulse is a nonreturn-to-zero (NRZ)-type pulse, whereas the second DAC pulse is a return-to-zero (RZ)-type pulse; this is accomplished using a current-steering DAC. In order to reduce mismatch without using a data-weighted averaging circuit, the size and layout of the unit current source in the current-steering DAC are considered carefully. The CT-DSM achieves a signal-to-noise ratio (SNR) of 67.3 dB, a signal-to-noise and distortion ratio (SNDR) of 63.4 dB, and a dynamic range of 75 dB for a 20-MHz signal bandwidth.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.