Tunable VHF Transconductor Using Double-Gate Carbon Nanotube Field Effect Transistors (DG-CNTFETs) and its Application in Gm-C Filters

Tunable VHF Transconductor Using Double-Gate Carbon Nanotube Field Effect Transistors (DG-CNTFETs) and its Application in Gm-C Filters

This paper presents a new tunable Operational Transconductance Amplifier (OTA) based on double-gate carbon nanotube field effect transistor (DG-CNTFET). The inverter-based OTA works with low supply voltage (1.0 V) and it is suitable for continuous-time filters in the VHF range. The tunability of this OTA is easily achieved by the control voltages of the DG-CNTFET’s back gates. The proposed OTA has no internal nodes and allows rail-to-rail input voltage swing. Based on the results of HSPICE simulations in the 32 nm process, the OTA has a dc gain of 81 dB. unity gain frequency (UGF) of the proposed OTA is 1.12 GHz and its phase margin is 90°. As a sample application, a second-order filter with low-pass and band-pass outputs was implemented based on the proposed OTA. Based on the simulation results, the DG-CNTFET-based filter can provide a frequency range of 68 kHz to 143 MHz with a tuning range greater than 160 times for low-pass response. The power consumption of the filter in the tuning range can vary from 0.17 μW to 9.7 mW depending on the required filtering range.