A comparison of GaAs HJBT and silicon bipolar technologies for high-speed analog-to-digital converters

The potential using the emerging GaAlAs/GaAs heterojunction bipolar transistor (HJBT) technology is all-parallel analog-to-digital (A/D) converters is studied. To put into perspective the HJBT predictions made, a comparison of the ultimate performance levels achievable with contemporary silicon bipolar processes is given. Optimized latched compensators were developed for each technology and simulations on SPICE were carried out to determine the maximum sample rate and large-signal analog bandwidths that would be achieved. As both technologies are produced in-house, models were available for processors in the latter stages of development, namely the standard 1-μm silicon bipolar process, and the 4-μm HJBT process, as well as processes at an earlier stage of development, the enhanced 1-μm silicon bipolar processes and the 2.5-μm HJBT process. This enabled the trend of performance improvements with time to be compared