In this paper, a simple macro model of n-channel MOSFET with dual workfunction gate (DWFG) structure is proposed. The DWFG MOSFET has higher transconductance and lower drain conductance than conventional MOSFET. Thus analog circuit design using the DWFG MOSFET can improve circuit characteristics. Currently, device models of the DWFG MOSFET are insufficient, so simple series connected two MOSFET model is proposed. In addition, a two stage operational amplifier using the proposed DWFG MOSFET macro model is designed to verify the model.

This paper presents a design and fabrication of 0.5 V two stage operational amplifier. The proposed operational amplifier utilizes body-driven differential input stage and self-cascode current mirror structure. Cadence Virtuoso is used for layout and the layout data is verified by LVS through Mentor Calibre. The proposed two stage operational amplifier is fabricated using 0.13 ㎛ CMOS process and operation at 0.5 V is confirmed. Measured low frequency small signal gain of operational amplifier is 50 ㏈, power consumption is 29 ㎼ and chip area is 75 ㎛ × 90 ㎛.