Design techniques for high-resolution current-mode sigma-delta modulators

14-bit DR, 20 kHz BW, 2-2 MASH SI-Σ㪔 modulator using low-distortion feedforward topology

“…Table I summarizes the simulated results and compares them with others SI-Σ∆M references. Although [9] has the highest DR, it requires very large memory capacitors (> 40 pF) and two single-ended modulators in a pseudo-differential configuration, which implies in a very complex architecture and chip area penalty. Now, using the following Figure-…”

Harmonic distortion in fully-differential switched-current sigma-delta modulators

“…Thus, even powers of the input current in (4) can be considered negligible. On the other hand, assuming that the third-order harmonic is dominant, (4) can be simplified into (5) In this case, the Total Harmonic Distortion ( ) is approximately equal to and given by (6) 3. Harmonic distortion in fully-differential SI integrators Fig.2 shows the schematic of a fully-differential LDI SI integrator.…”

“…Performances reported to date for SI Σ∆Ms are lower than for state-of-the-art SC Σ∆Ms [7]. For instance, [5] obtains 13-bit for lowpass voice band signals, while [6] obtains 9-bits for bandpass signals in the AM bandwidth. Among other reasons, such lower performances are motivated by larger influence of SI non-idealities, as compared to SC ones, and by incomplete modeling of their influence [8] [9][10] [11].…”

“…This is the case of switched-current circuits (SI) [1], which during the last ten years have been used for different analog functions, including filtering [2] and A/D conversion [3]. Particularly, several SI Σ∆Ms have been reported, for lowpass signals [4] [5], as well as for bandpass signals [6].…”

Switched-current ΣΔ modulator for baseband channel applications

“…Although some switched-current EA modulators have appeared in the literature [6], [7] they were either of low order or worked with relatively low sampling frequencies. So far, there has not been an attempt to target high bandwidth applications such as the baseband channel conversion in wireless receivers.…”