A Design of a Low-Voltage Current-Mode Fully-Differential Analog CMOS Integrator Using FG-MOSFETs and Its Implementation

In the field of analog signal processing, there is a strong need for low-voltage and low-power integrated circuits. Especially in the mobile communication circuitry, an analog signal processing circuit must be fed by dry batteries of 1–1.5 V. This paper presents a design and implementation of a current-mode fully-differential analog CMOS integrator operable with such a low supply voltage. This integrator is built with a cross-coupled matched pair of 3-input FG(Floating Gate)-MOSFETs, a matched pair of 2-input FG-MOSFETs, and four bias current sources. In this circuit, both a low apparent threshold voltage of FG-MOSFETs and voltage signal summation at the floating gates are effectively utilized to enable the circuit operation with a low supply voltage and to simplify the circuit configuration. The influence of the common-mode signal and noise to the signal processing are minimized by adopting fully-differential structure. The performance of the proposed integrator circuit is predicted by theoretical analysis and by HSPICE simulations. The circuit works as an integrator in the frequency range 4–750 MHz at a 1.5 V supply voltage and dissipates DC power of about 70 μW. The proposed circuit was fabricated by a Motorola 1.2 μm double-poly CMOS process in the chip fabrication program of VLSI Design and Education Center (VDEC).