A 0.5-V 74-dB SNDR 25-kHz Continuous-Time Delta-Sigma Modulator With a Return-to-Open DAC

Low-Power Low-Voltage ΔΣ Modulator Using Switched-Capacitor Passive Filters

“…Utilizing advanced switches developed to date, the switch overdriving problem can simply be alleviated. Low-VTH switch [8,14], gate-boosted [15][16] or boot-strapped switches [17] are several examples of such modern switches. Energy harvesting and biomedical implant systems are two applications where ultra low-voltage circuit design is compulsory and highly demanding.…”

“…Conventional analog circuit topologies are no longer useful in these systems. Therefore, new circuit techniques have been developed recently, which have enabled ultra low-voltage operation of the  ADCs [15][16]. Body-input operational transconductance amplifiers (OTAs) and body-input gateclocked comparator operating at 0.5 V in [15] eliminated the constraint on the threshold voltage.…”

“…Therefore, new circuit techniques have been developed recently, which have enabled ultra low-voltage operation of the  ADCs [15][16]. Body-input operational transconductance amplifiers (OTAs) and body-input gateclocked comparator operating at 0.5 V in [15] eliminated the constraint on the threshold voltage. Moreover, inverter-based integrators were realized by overdrive voltages near the VTH in the modulator presented in [16] using a switched-capacitor (SC) biasing scheme, where charge pump clock boosting scheme were utilized for sufficient switch overdrive.…”

“…The passive modulator presented in [3] with 0.43 µW power consumption and medium resolution (68 dB SNR from a 0.7 V power supply) looks attractive when using FOMW definition, as given by equation (15). When considering FOMS, the hybrid second-order and fourth-order modulators present the FOM of 156.5 and 175, respectively, which demonstrate high power-efficiency among the modulators [2][3][4][5][6].…”

A 300-mV ΔΣ Modulator Using a Gain-Enhanced, Inverter-Based Amplifier for Medical Implant Devices

“…There are two critical factors that can determine the lowest operating power supply of the traditional sigma-delta (∆Σ) modulators: operational transconductance amplifiers (OTAs) in the integrators and the adequate driving voltage of the switching transistors [8][9][10][11][12][13][14]. The conventional analog circuit topologies are no longer practical in ultra-low-voltage operations (below 0.6 V), and also, stacking more than two transistors is impossible due to the limited overdrive and voltage headroom.…”