# A 90.9 dB SNDR 95.3 dB DR Audio Delta–Sigma Modulator with FIA-Assisted OTA

## TL;DR

This paper introduces a power-efficient audio modulator design that achieves high performance in terms of signal quality and dynamic range.

## Contribution

A novel FIA-assisted OTA integrator design that improves gain and reduces power consumption by 30% compared to traditional cascode designs.

## Key findings

- The proposed integrator achieves 80 dB gain with 30% lower power consumption.
- The delta–sigma modulator achieved 90.9 dB SNDR and 95.3 dB DR while consuming 221 µW.
- The design simplifies the feedback DAC without using mismatch shaping techniques.

## Abstract

This paper presents a low-power, high-gain integrator design that uses a cascode operational transconductance amplifier (OTA) with floating inverter–amplifier (FIA) assistance. Compared to a traditional cascode, the proposed integrator can achieve a gain of 80 dB, while reducing power consumption by 30%. Upon completing the analysis, the value of the FIA drive capacitor and clock scheme for the FIA-assisted OTA were obtained. To enhance the dynamic range (DR) and mitigate quantization noise, a tri-level quantizer was employed. The design of the feedback digital-to-analog converter (DAC) was simplified, as it does not use additional mismatch shaping techniques. A third-order, discrete-time delta–sigma modulator was designed and fabricated in a 0.18 μm complementary metal-oxide semiconductor (CMOS) process. It operated on a 1.8 V supply, consuming 221 µW with a 24 kHz bandwidth. The measured SNDR and DR were 90.9 dB and 95.3 dB, respectively.