Design of a CMOS differential difference amplifier and its applications in A/D and D/A converters

The differential difference amplifier (DDA) is an extension of an opamp with two differential inputs. DDA-based circuits often provide high input impedance and simple external circuitry due to the feature of differential difference inputs. Therefore, DDA-based circuits are competitive alternatives to opamp-based circuits. In this paper, we will present the design of a DDA using a proposed linear V-I converter whose linearity is improved by the body effect. This DDA possesses almost rail-to-rail input common-mode range and output swing and is therefore suitable for low-voltage applications. The DDA was fabricated in a MOSIS 2 μm p-well process, and its simulation and experimental results are provided. Applications in A/D and D/A converters are discussed