The algebraic differentiators introduced by Mboup, Join and Fliessare studied in the frequency domain. The study complements the time-domain developments of the previous reference where a least-squares interpretation has allowed to explain the main properties of the method and also to devise efficient differentiators. The frequency-domain analysis gives answers to the central question of the choice of the algebraic differentiator parameters. Also, an interpretation of the algebraic differentiators in terms of wavelet decomposition is given.