A Single-Opamp Third Order CT Δ Σ Modulator With SAB-ELD-Merged Integrator and Three-Stage Hybrid Compensation Opamp

This paper proposes a 3rd order continuous-time delta-sigma modulator (CTDSM) with a single amplifier biquad (SAB) and excess loop delay (ELD) merged integrator. The integrator enables a 2nd order noise-shaping together with ELD compensation with just a single Opamp and feedback DAC. A three-stage Opamp with a hybrid frequency-compensation scheme is presented, which achieves high gain and large unity-gain bandwidth (UGBW) with low power. The circuit secures an extra order noise-shaping through a passive noise-shaping SAR (NS-SAR) quantizer (QTZ) while further incorporating a preliminary sampling and quantization (PSQ) technique, the 1st order NS QTZ can run at 1.5 GHz with 6b. The design, implemented in 28 nm, obtains 74.4 dB SNDR with 50 MHz bandwidth while consuming 10.4 mW from 1.5 V and 1 V power supplies. The prototype attains a dynamic range of 80.6 dB with a Schreier FOM of 171.2 dB. With the presented integrator and Opamp, the loop filter only consumes 14 % of the total DSM power consumption.