High-speed ADC systems with HBTs for measuring instrument applications
This paper presents very high-speed Analog-to-Digital Converter (ADC) systems for measuring instrument applications, and also related theoretical results. First we describe the design, testing and performance of ?1 GS/s 6-bit and 7-bit ADCs using SiGe heterojunction bipolar transistor (SiGe HBT), and a 3 GS/s 6-bit ADC and Track/Hold (T/H) circuit using GaAs heterojunction bipolar transistor (GaAs HBT). We show that SiGe HBTs and GaAs HBTs have technological potential, and that the folding/interpolation architecture is suitable for high-speed ADC systems. Next, we derive three theoretical results aimed at very high-speed, wideband ADC systems. ?A folding/interpolation architecture is suitable for very high-speed ADCs implemented with HBTs, and digital error correction is required to improve their AC performance. We show an error correction algorithm, as well as its effectiveness and limitation for high-frequency inputs. ?Aperture jitter is crucial in wideband ADC systems, and we have derived very general results about aperture jitter effects of such systems. ?A time-interleave ADC system can realize very high-speed ADC system, but timing skews in the system degrade its overall accuracy. We have derived the error power corresponding to timing skews. Finally, we discuss several issues relating to standardizing the specifications of very high-speed ADCs targeted at measuring instrument applications.
adc hbt error correction jitter t/h circuit