Design, simulation and comparative analysis of CNT based cascode operational transconductance amplifiers.

Area of Science:

• Electronics
• Materials Science
• Semiconductor Devices

Background:

• Conventional CMOS-based cascode operational transconductance amplifiers (COTAs) face limitations in performance metrics like gain, power consumption, and stability.
• Carbon nanotube field-effect transistors (CNTFETs) offer potential advantages over traditional MOSFETs due to their unique electrical properties.
• Investigating CNTFETs in COTA configurations is crucial for advancing analog circuit design.

Purpose of the Study:

• To design and simulate CNTFET-based COTAs and compare their performance against conventional CMOS-based COTAs.
• To evaluate the impact of cascoding on CNTFET-based OTA performance.
• To analyze the influence of CNTFET structural parameters (number, pitch, diameter) on COTA performance.

Main Methods:

• Three CNTFET-based COTA structures were designed and simulated using HSPICE.
• Designs included pure CNTFET and hybrid CNTFET-MOSFET configurations.
• Performance metrics such as DC gain, output resistance, slew rate, power consumption, phase margin, gain margin, and rejection ratios were evaluated and compared.

Main Results:

• CNTFET-based COTAs significantly outperformed CMOS-based COTAs, with a pure CNT-based COTA showing an 81.4% increase in DC gain and 324 times lower power consumption.
• Cascoding in CNTFET-based OTAs led to a 12.5% increase in gain and a 13.07% increase in output resistance.
• Optimizing CNTFET parameters (N, S, DCNT) demonstrated potential for further performance enhancement.

Conclusions:

• CNTFETs are highly promising for developing high-performance, low-power COTAs.
• The cascode configuration further boosts the performance of CNTFET-based amplifiers.
• Careful selection of CNTFET structural parameters is key to maximizing COTA efficiency and performance.