ADC preamplifier works the gain/dynamic-range trade-off to achieve 14-bit linearity

摘要

System designers in many fields continually strive to increase the speed and precision in their analog-signal-processing chain by upgrading the ADC (Figure 1). In the ADC realm, the units of speed and precision are samples per second and effective number of bits, respectively. Unfortunately, a designer cannot increase the speed and precision of an analog-signal-processing chain by merely using a better data converter, because the quality of the input signal can limit converter performance. For this reason, the designer must give equal attention to the design of the ADC preamplifier to maximize the performance of the system. The design of an ADC preamplifier revolves around noise and distortion. Noise and distortion represent undesirable signal content that can degrade the performance of the entire signal-processing chain. If the gain block before the ADC contributes noise or distortion at or near the power levels of the ADC's minimum detectable signal, the undesirable signal content can mask the presence or absence of real signal information and effectively reduce the precision of the signal.