Designing High Speed Analog Signal Chains from DC-to-Wideband
All the rage these days in the converter world is the GSPS ADC—otherwise known as an RF ADC. With such high sample rate converters available on the market this opens up the Nyquist by 10× as compared to five years ago. A lot has been discussed about the advantages of using RF ADCs and how to design with them and capture data at such high rates. Thank you JESD204x consortium. But one consideration seems to be forgotten about, the lowly DC signal. The design of the input configuration, or front end, ahead of a high performance, analog-to-digital converter (ADC) is always critical to achieving the desired system performance. Typically the focus is capturing wideband frequencies, such as those greater than 1 GHz. However, in some applications, DC or near DC signals are also required and can be appreciated by the end user, as they too carry important information. In this paper, an overview on the importance of common-mode signals and how to properly level shift the amplifier front end will be presented in a real system solution example.