[1]
F. S, oval-Ibarra., and R. Rodríguez-Calderón, “A CMOS transistor-only $\mathbf{2^{nd}}$ order low-pass $\mathbf{\Sigma \Delta}$ modulator”, Rev. Mex. Fís., vol. 49, no. 4, pp. 303–0, Jan. 2003.