Carbon nanotube CMOS analog circuitry

Abstract

Carbon nanotube (CNT) field-effect transistors (CNFETs) promise significant energy efficiency benefits versus today's silicon-based FETs. Yet despite this promise, complementary (CMOS) CNFET analog circuitry has never been experimentally demonstrated. This work presents the first reported demonstration of CNFET CMOS analog circuits. For characterization, we fabricate analog building-block circuits such as multiple instances of two-stage op-amps. These CNFET CMOS op-amps achieve gain >700, operate at a scaled sub-500 mV supply voltage, achieve high linearity, and are robust over time. Additionally, we demonstrate a front-end analog sub-system that integrates a CNFET-based breath sensor with an analog sensor interface circuit (transimpedance amplifier followed by a voltage follower to convert resistance change of the chemoresistive CNFET sensor into a buffered output voltage). However, further progress in large-scale CNFET analog circuits is difficult to realize due to the inherent presence of metallic-CNTs (m-CNTs), which create an electrical short between the source and drain of a transistor and can result in excessive leakage current and severe degradation to analog circuit performance. Self-Healing Analog with RRAM and CNFETs (SHARC) is a novel circuit technique that leverages the programmability of resistive random-access memory (RRAM) to overcome the presence of m-CNTs for analog circuits. Here, we experimentally validate SHARC for multiple analog and mixed-signal circuit topologies. Using SHARC, we experimentally demonstrate the first mixed-signal and complex analog circuits fabricated with CNFETs.