A wide range differential difference amplifier: a basic block for analog signal processing in MOS technology

A CMOS implementation of a wide-input-range differential difference amplifier (DDA) using a V-I converter with large signal handling capability is presented. The DDA is used as a basic building block for continuous-time analog signal processing systems. The basic features of the DDA are verified experimentally using a 2-μm CMOS process MOSIS chip. It is shown that it is generally possible to develop DDA-based analog circuitssth almost infinite input impedances, low component count and without the need to match components/devices external to the DDA. DDA-based circuits such as amplifiers, a MOS grounded resistor, four quadrant multipliers and amplitude modulators are presented. Applications of the DDA in the implementation of frequency selective circuits, e.g., resonator and state-variable second-order filters, are also given. All proposed circuits and design techniques are experimentally verified and demonstrate that DDA-based circuits offer a competitive alternative to op-amp-based circuits