A novel double sampling technique for delta-sigma modulators

The double sampling technique is used to achieve twice the sampling frequency in sampled-data systems without extra requirements (e.g., clock rate, op-amp settling time, op-amp dc gain, etc.). In this paper, theoretical analyses of the effects of nonidealities (integrator leakage, path gain mismatch and non-uniform sampling) on the performance of double sampling delta-sigma modulators (ΔΣM´s) are given. A novel double sampling technique for ΔΣM´s which is insensitive to the path gain mismatch is also presented. This technique uses a bilinear integrator in the first stage, resulting in a first order shaping of the path gain mismatch error. Compared with a second-order single sampling ΔΣM, this technique is able to achieve 15 dB improvement of S/N and 6 dB relaxation of op-amp dc gain