ADC resolution is often the first specification engineers check, but real system accuracy is shaped by noise, linearity, sampling architecture, and external circuitry. In a signal chain that includes converters, amplifiers, RF functions, and power devices, a high-resolution ADC may still underperform if the driver amplifier is not suitable or the voltage reference is noisy. High-speed designs must account for clock jitter, input bandwidth, and layout parasitics, while precision low-speed designs need attention to drift, common-mode range, and interference rejection. A better method is to derive the signal chain from sensor range, bandwidth, error budget, isolation needs, and power constraints.