Carbon Nanotube Quantum Capacitance for Nonlinear Terahertz Circuits

In this paper, analog circuit applications of a nonlinear carbon nanotube (CNT) quantum capacitance such as frequency doublers and mixers are proposed. We present a balanced circuit implementation and derive the transconductance conversion gain for the nonlinear CNT quantum capacitor circuit. The balanced topology results in robust circuit performance that is insensitive to extrinsic capacitances and parasitic resistances, and is immune to the resistance of metallic nanotubes that may be in the channel. The ballistic quantum capacitance is useful up to several terahertzs (THzs), making it suitable for low-noise THz sources. Additionally, the fundamental bandwidth and performance limitations imposed by the quantum conductance and inductance are discussed.