A High-Linearity Sigma-Delta Topology Suitable for Low-Voltage Applications

A Sigma-Delta topology with reduced sensitivity to OTA gain nonlinearities has been introduced. The most important feature of this topology is that the signal transfer function is unity, which is relatively independent to the building block characteristics. With careful signal scaling, signal swings inside the loop can be suppressed to less than 50% of the reference voltage, which is highly appreciated by low-voltage designs. Behavior simulation revealed that requirements for OTA are quite relaxed in this topology. With an oversampling ratio of 128, the proposed thirdorder modulator topology can achieve more than 16 bit resolution. Simulated with a 90nm CMOS technology file, more than 96dB SNR can be achieved with less than 0.5mW power dissipation in 20kHz signal bandwidth under 1 volt power supply voltage