Electronic Design

Complementary SiGe BiCMOS Facilitates Precision High-Speed Analog

To extend its BiCOM biCMOS process into the next generation, Texas Instruments is tapping the benefits of complementary silicon-germanium (SiGe) bipolar transistors. TI has developed a third generation of fully isolated complementary SiGe biCMOS, or BiCOM III, for ultra-high-speed precision analog and mixed-signal ICs.

This development im-proves speed nearly threefold and reduces noise by 50% in operational amplifiers over the previous generation. The process boasts fully dielectric isolated 5-V poly-emitter npn and pnp bipolars matched within a factor of two.

While the transition frequency (fT) for the bipolar transistors is in the 15- to 20-GHz range, the maximum frequency (fMAX) values span from 40 to 50 GHz. Besides well matched transistors, the BiCOM III also furnishes high gain times Early voltage (ß ×VA) and transition frequency times collector-to-emitter breakdown voltage (fT × BVCEO) characteristics (see the table).

Conventionally, increasing VA comes at the expense of fT. But this effect is offset by the SiGe biCMOS process, which reduces the parasitic capacitance and increases the mobility of the transistors.

The biCMOS process integrates 5-V CMOS circuits for dense digital functions. To support system-level integration, it incorporates stable high-performance passives. This includes precision metal-insulator-metal (MIM) capacitors, poly and thin-film precision resistors, metal fuses, and triple-level metal interconnects. Using this process, TI has fabricated and characterized a 2.3-GHz voltage feedback amplifier with a gain of 5 and a third-order intermodulation distortion (IMD3) of −90 dB at 100 MHz.

Developed at TI's facilities in Freising, Germany, and presently under qualification, the process is expected to go into volume manufacturing by the end of the year. TI plans to exploit it for next-generation ultra-fast high-resolution data converters, current-feedback amplifiers, and other mixed-signal ASICs that were not beyond the prowess of early-generation processes. Visit www.ti.com for details.

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