A Theoretical Investigation into the Limits of Bandwidth Enhancement with the Asymmetrical Bridged T-Coil Network

ABSTRACT

This paper presents the results of a theoretical investigation of the asymmetrical bridged T-coil (BTC) bandwidth enhancement network under the condition of maximally flat magnitude (MFM) response. Conventionally, the BTC is used in the symmetrical configuration and it is well known that, as compared to the commonly used RC load, the maximum bandwidth enhancement ratio (BWER) under the MFM condition is 2√2. It is shown here that by introducing asymmetry, even under the constraint of MFM response, the maximum achievable BWER is theoretically unlimited, the limit being set only by practical considerations. Unlimited BWER has never been considered possible, even theoretically, with BTC or any other network, and the result reported here is believed to be a breakthrough in the design of wide-band and ultra wide-band amplifiers.

Simulations for a few designs indicate that practical realization of the full potential of the asymmetrical BTC may have to wait for improved technologies which facilitate tight coupling between the two parts of the coil and also minimize parasitic effects.

KEYWORDS:

• Bandwidth enhancement
• bridged T-coil
• maximally flat magnitude
• wide-band amplifiers

Acknowledgements

This work was supported by the Indian National Science Academy through the Honorary Scientist scheme. The author is thankful to Y. V. Joshi, S. K. Koul, R. Bhattacharya, and G. Chowdary for their help in preparing the manuscript.

Disclosure statement

No potential conflict of interest was reported by the author.

Additional information

Notes on contributors

Suhash C. Dutta Roy

S. C. Dutta Roy received his bachelor's, master's, and doctorate degrees from the University of Calcutta, Calcutta, India, in 1956, 1959, and 1965, respectively. He was a lecturer at the University of Kalyani, West Bengal, India, for five years before taking up an assistant professor's position at the University of Minnesota, Minneapolis, Minnesota, USA. He returned to India in 1968 and spent more than four decades at the Indian Institute of Technology Delhi (IITD) as an associate professor, professor, head of the department, and dean of undergraduate studies. On sabbatical leave from IITD, he spent a year at the University of Leeds, UK, and another year at the Iowa State University, Ames, Iowa, USA, as a visiting professor. Upon superannuation from IITD, he continued there first as an emeritus fellow, then as a senior scientist of the Indian National Science Academy (INSA), and finally as an honorary scientist of the INSA. Currently, he continues working from home as INSA honorary scientist.

Professor Dutta Roy's research interests are in circuits, systems, and signal processing. He has published more than 260 research papers in IEEE, IEE, and other reputed journals and transactions, and has mentored 30 PhD students. He holds one US and three Indian patents and is the creator of five highly popular full-length video courses, four of which are available on the YouTube for free downloading. His research has been recognized by fellowship of the IEEE and of all the National Academies of Science and Engineering of India, and a distinguished fellowship of the Institution of Electronics and Telecommunication Engineers, New Delhi, India, and several national awards, including the most prestigious Shanti Swarup Bhatnagar Prize.

E-mail: [email protected]