The technological aim of the TARANTO EU project is to develop heterojunction bipolar transistors (HBTs) with a maximum oscillation frequency of fmax = 600 GHz. These HBTs are embedded into modern high integration CMOS processes like 130 nm or 90 nm from Infineon and 55 nm or 28 nm from ST Microelectronics. IHP is working on maximum oscillation frequencies of 700 GHz.
Within the TARANTO project, INT is responsible for design, layout and characterization of ultra-fast front-end input circuits for analog-to-digital converters. We use modern high-speed BiCMOS processes of the technology nodes of 130 nm and 90 nm. To reach sampling rates beyond 100 GS/s with high bandwidth, we apply the principle of fourfold synchronous time interleaving. The principle is illustrated in the following figure. A clock divider generates a four-phase clock that controls four time-interleaved track-and-hold circuits. We use two different approaches for the design of the track-and-hold circuits: voltage mode, where the sampled input voltage is stored on a hold-capacitor and current mode, where the input current accumulates a charge on a resettable hold-capacitor.
Further chips for single critical components, like track-and-hold circuits and broadband amplifiers, as well as complete 1-to-4 interleaver-ICs at more than 100 GS/s have also been designed and fabricated.
- F. Buchali, X.-Q. Du, K. Schuh, S. T. Le, M. Grözing, and M. Berroth, “A SiGe HBT BiCMOS 1-to-4 ADC frontend enabling low bandwidth digitization of 100 GBaud PAM4 data,” Journal of Lightwave Technology, vol. 38, no. 1, pp. 150--158, 2020.
- S. T. Le, K. Schuh, F. Buchali, X.-Q. Du, M. Grözing, M. Berroth, L. Schmalen, and H. Bülow, “Single Sideband Transmission Employing a 1-to-4 ADC Frontend and Parallel Digitization, invited paper,” Journal of Lightwave Technology, vol. 38, no. 12, pp. 3125--3134, 2020.
- X.-Q. Du, M. Grözing, A. Uhl, S. Park, F. Buchali, K. Schuh, S. T. Le, and M. Berroth, “A 112-GS/s 1-to-4 ADC front-end with more than 35-dBc SFDR and 28-dB SNDR up to 43-GHz in 130-nm SiGe BiCMOS,” in IEEE Radio Frequency Integrated Circuits Symposium (RFIC), Boston, MA, USA, 2019, pp. 215--218.
- X.-Q. Du, M. Grözing, and M. Berroth, “A 25.6-GS/s 40-GHz 1-dB BW Current-Mode Track-and-Hold Circuit with more than 5-ENOB,” in IEEE 2 BiCMOS and Compound Semiconductor Integrated Circuits and Technology Symposium (BCICTS), San Diego, CA, USA, 2018, pp. 56--59.