A 0.5-V Multiple-Input Bulk-Driven OTA in 0.18-μm CMOS

This article presents the experimental results for a multiple-input operational transconductance amplifier (MI-OTA). To achieve extended linearity under 0.5-V low voltage supply, the circuit employs three linearization techniques: the bulk-driven (BD), the source degeneration, and the input voltage attenuation created by the MI metal-oxide-semiconductor transistor technique (MI-MOST). Although the linearization techniques result in reduced dc gain, the self-cascode transistors are used to boost the gain of the MI-OTA. Furthermore, the MI-MOST simplifies the internal structure of the OTA and may reduce the complexity of the applications. The MI-OTA operates in the subthreshold region and offers tunability by a bias current in the nanoampere range. The circuit is capable to work with 0.5-V supply voltage while consuming 24.77 nW. The circuit was fabricated using the 0.18- $\mu \text{m}$ Taiwan Semiconductor Manufacturing Company (TSMC) CMOS technology and it occupies a 0.01153-mm2 silicon area. Intensive simulation and experimental results confirm the benefits and robustness of the design.