What Exactly is a Low drift sample and hold?

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Discussion Overview

The discussion revolves around the concept of a low drift sample and hold circuit, particularly in the context of its application in digital control systems. Participants explore the meaning of "low drift" and the factors that contribute to it.

Discussion Character

  • Technical explanation, Conceptual clarification

Main Points Raised

  • One participant notes that a sample and hold circuit is used to maintain a steady analogue value during operations performed by a converter or other systems.
  • Another participant suggests that "low drift" implies that the output remains stable during the hold time compared to previous units, indicating improved performance.
  • A further contribution outlines that achieving low drift requires a capacitor with low leakage, low dielectric absorption, and a high-impedance input to the buffer amplifier in the sample and hold circuit.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the specific implications of low drift, but there is agreement on the factors that contribute to achieving it.

Contextual Notes

There may be limitations related to the definitions of "drift" and the specific performance metrics of sample and hold circuits that are not fully explored in the discussion.

Ian_Brooks
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I realize a sample and hold is used in digital control whereby the circuit holds the analogue value steady for a short time while the converter or other following system performs some operation over that held time.

However what does it mean by having low drift?
 
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You won't find anyone specifying a high drift sample and hold. It means the output doesn't change as much during the hold time as previously manufactured units in the same class.
 
For low drift, you need a capacitor with low leakage (easy), low dielectric absorption (need the right material), and you need a high-impedance input to the buffer amp in the S/H.
 
thanks
 

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