A simple circuit for sigma-delta/delta modulation

This article represents a simple circuit which can function either as sigma-delta or delta modulation. The circuit is composed of three OTAs, a capacitor and two resistors which basically form Schmitt-trigger circuit When input signal is present and fed to the inverting input node of OTA1, the circuit acts as a sigma-delta modulation. Contrarily, without adding any component, the same circuit functions as delta modulation when input signal is instead fed to a resister R/sub 1/ node. In addition, frequency and amplitude of the modulated signal not only are independently adjusted but also these characteristics are electrical tuned. Based on the compactness of the proposed circuit, it is therefore suitable for IC realization. The computer simulation results are illustrated to confirm with die given circuit analysis.