A 3rd-Order Single-OTA Σ-Δ Modulator for Low-Power Mixed-Signal System-on-Chip Applications

Inhalt:
This paper brings forward a 3rd-order single operational transconductance amplifier (OTA) σ-δ analogue-to-digital (A/D) modulator as a means to achieve low-power A/D conversion on mixed-signal system-on-chip (SoC) designs. The proposed concept is based on the utilisation of a single OTA within the modulator structure which is shared in time in order to perform concurrently sampling and integration. Thus, power consumption as well as on-chip area can be saved since only one OTA is used. The paper also discusses the impact of non-idealities (e.g. finite gain and bandwidth of the OTA, noise folding, switch on-resistance, etc.) on the performance of the proposed modulator. A prototype of the 3rd-order modulator based on a 0.35 µm CMOS technology is presented in order to prove the correctness of the proposed concept.