Nonlinear-stability analysis of higher order ∆ –Σ modulators for DC and sinusoidal inputs

Abstract

The maximum stable input limits for third-, fourth-and fifth-order Chebyshev Type II based Δ-Σ modulators are established using the Describing Function Method for DC and sinusoidal inputs. Closed-form mathematical expressions for the gains of the quantizer for higher-order Δ-Σ modulators whose inputs are two concurrent sinusoids are derived from first principles. The derived stability curves are shown to agree reasonably well with the simulation results for different types of input signals and amplitudes.