Sample-and-hold (S/H) performance specifications: Which of the following parameters is specifically defined for a sample-and-hold circuit used ahead of an ADC in mixed-signal systems?

Introduction:
Sample-and-hold (S/H) circuits are placed in front of analog-to-digital converters (ADCs) to freeze the input long enough for accurate conversion. Understanding the vocabulary of S/H performance—such as acquisition time, aperture time, aperture jitter, droop rate, and hold step—is essential for specifying dynamic signal-chain behavior and error budgets.

Given Data / Assumptions:

• An S/H captures a snapshot of an analog input and holds it momentarily.
• We are identifying a parameter that is formally defined for S/H operation.
• Terminology should match standard datasheet usage.

Concept / Approach:
Key S/H terms: acquisition time (time to settle during sampling), aperture time (effective sampling instant width during which the input is transferred to the hold capacitor), aperture jitter (timing uncertainty of that instant), droop rate (rate of held voltage decay), and hold step (voltage step at sample/hold transition). Of the offered options, “aperture time” is a canonical S/H spec. “Aperture droop” and “acquisition jitter” are not standard terms; “feedback” is not a defining S/H spec.

Step-by-Step Solution:

Verification / Alternative check:
Check any high-speed ADC front-end S/H datasheet: you will find “aperture time” and “aperture jitter” explicitly listed; you will not find “acquisition jitter” or “aperture droop” as formal specs.

Why Other Options Are Wrong:

• Aperture droop: Non-standard phrasing; “droop rate” is the correct S/H term.
• Feedback: Generic circuit concept, not an S/H performance metric.
• Acquisition jitter: Non-standard; “acquisition time” exists, “aperture jitter” exists.

Common Pitfalls:
Confusing aperture time (sampling window) with acquisition time (settling time), or using inconsistent terminology that does not appear in datasheets, which leads to miscommunication with vendors and design teams.

Final Answer:
Aperture time