A Hybrid A/D Converter with 120dB SNR and -125dB THD

Recent 18 to 24 bit ADCs, especially for audio applications, require an excellent signal to noise ratio (SNR) performance and an excellent total harmonic distortion (THD) performance at the same time. Moreover, most of applications require precision DC performance. To achieve excellent SNR performance, a multi-bit delta-sigma (DeltaSigma) ADC is quite popular and it can be seen in the instruments or in many precision digitizers in ATE systems. However, it is well known that a successive approximation (SAR) ADC provides better THD performance than a multi-bit DeltaSigma ADC. Therefore, it is difficult to simultaneously achieve both excellent SNR performance and excellent THD performance with available ADCs in the market. This paper proposes a new hybrid ADC architecture which simultaneously provides excellent DC, SNR, and THD performance.