Transformer based inter-stage coupling scheme for amplifiers


Amplifiers are indispensable for systems and impose significant challenges for on-chip mm-Wave/THz systems, including power amplifiers in the transmitter and low noise amplifiers in the receiver. High amplifier performances are hard to achieve due to the large losses of inter-stage matching network.  The performance degradation are induced by different factors, such as circuit biasing networks, simulation inaccuracy introduced non-optimal design, on-chip crosstalk. We have invented the transformer based inter-stage matching scheme to effectively address all the critical issues for on-chip mm-Wave/THz amplifiers with several prominent advantages. First, it provides inherent DC blocking between stages to allow individual optimum biasing for each stage. Second, it supports flexible voltage/current gain performance by adjusting the winding turns ratio to enable active/passive co-optimization. Third, the natural inter-stage T matching network accomplishes impedance matching with symmetrical configurations and immunity to on-chip coupling noises with fully differential configuration. Fourth, physically spanned input and output signals benefits good isolation and compact physical design minimizes losses; Fifth, differential structure facilitates accurate performance estimation through EM simulations and design optimization. This method has been widely used by many other groups.

With the invented transformer based inter-stage matching, we have demonstrated a series of high performance mm-wave CMOS amplifiers, starting from a 60 GHz power amplifier (PA) with the gain > 30 dB, a 100 GHz PA with the highest saturated output power Psat about 15 dBm in CMOS and a 100 GHz Low Noise Amplifier (LNA) with the best noise figure (NF) of < 8 dB in 2012, then a wideband 128-157 GHz amplifier with the power gain higher than 10 dB, to the fastest amplifier at 200 GHz with the maximum gain about 8 dB in 2012, all in CMOS technologies. We have published 17 papers and filed 1 patent disclosure in this domain.



  1. Y. Ye, B. Yu, X. Ding, X. Liu, and Q. J. Gu, “High Energy-Efficiency High Bandwidth-Density Sub-THz Interconnect for the Last-Centimeter Chip-to-Chip Communications,” IEEE International Microwave Symposium IMS2017
  2. Y. Ye, B. Yu, and Q. J. Gu, “A 165GHz OOK Transmitter with 10.6% Peak DC-to-RF Efficiency in 65nm Bulk CMOS,” IEEE International Microwave Symposium 2016
  3. Y.-T. Chang, Y. Ye, C. Domier, and Q. J. Gu, “A Ultra-Wideband CMOS PA with Dummy Filling for Reliability,” 2015 IEEE International Wireless Symposium
  4. D. Huang, R. Wong, Q. Gu, N. Wang, T. Ku, C. Chien, and M.F. Chang, “A 60GHz CMOS Differential Receiver Front-End Using On-Chip Transformer for 1.2 Volt Operation with Enhanced Gain and Linearity,” IEEE Symposium on VLSI Circuits, pp. 144-145, June 2006.
  5. Y.-C. Liu, Q. J. Gu, T. LaRocca, N.-Y. Wang, Y.-C. Wu, and M.-C. F. Chang, “A 60 GHz High Gain Transformer-Coupled Differential Amplifier in CMOS,” Asia-Pacific Microwave Conference (APMC), pp. 932-935, November 2010, Best Student Paper Award
  6. Y-C. Liu, A. Tang, N.-Y. Wang, Q. J. Gu, R. Berenguer, H.-H. Hsieh, P.-Y. Wu, C. Jou, and M.-C. F. Chang, “A V-band Self-Healing Power Amplifier with Adaptive Feedback Bias Control in 65 nm CMOS,” IEEE Radio Frequency Integrated Circuits Symposium (RFIC) 2011
  7. Z. Xu, Q. J. Gu, and M.-C. F. Chang, “A 100-117GHz W-band CMOS Power Amplifier with On-Chip Adaptive Biasing,” IEEE Microwave and Wireless Components Letters, vol. 21, no. 10, pp 547-549, Oct. 2011
  8. Z. Xu, Q. J. Gu, and M.-C. F. Chang, “A Three Stage, Fully Differential 128 – 157 GHz CMOS Amplifier with Wide Band Matching,” IEEE Microwave and Wireless Components Letters, vol. 21, no. 10, pp 550-552, Oct. 2011
  9. J. Gu, Z. Xu, and M.-C. F. Chang, “Two-Way Current Combining W-Band Power Amplifier in 65 nm CMOS,” IEEE Transactions on Microwave Theory and Techniques, vol. 60, no. 5, pp. 1365-1374, May 2012
  10. Tang, D. Murphy, F. Hsiao, Q. J. Gu, Z. Xu, G. Virbila, Y.-H. Wang, H. Wu, L. Nan, Y.-C. Wu, and M.-C. F. Chang, “A CMOS 135-150 GHz 0.4 dBm EIRP Transmitter with 5.1dB P1dB Extension Using IF Envelope Feed-Forward Gain Compensation,” 2012 IEEE MTT-S International Microwave Symposium, June 2012, Honorable Mention Student Paper Award

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