# IEC sample-and-hold element

Canonical URL: https://eloragrid.ai/symbols/iec-sample-and-hold
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: S/H
Drawing use: Schematic
Reference families: IEC, Manufacturer

## Symbol convention

Convention: IEC
Form: Rectangular analogue element with S/H function and a digital control input
Qualifying-symbol and dependency conventions as explained in TI's public overview of IEEE Std 91-1984, which incorporates IEC 617-12 work. Independent educational drawing; not certified IEC geometry or an IEC database identifier. The counterpart is the matching functional concept; no equivalence of every detailed standard graphic is asserted.
Related representation: [Sample-and-hold amplifier](https://eloragrid.ai/symbols/sample-and-hold-amplifier)

Analogue element marked S/H with a digital control input; it tracks the input, then holds the last value.

## In plain English

### What does IEC sample-and-hold element mean?

The sample-and-hold element has an analogue input, an analogue output and a digital control input. While the control is in the sample state the output follows the input; when it changes to hold, the output keeps the last value. IEC-style analogue diagrams mark the digital control input with a # sign, as TI's overview describes for digital inputs on analogue symbols.

### A simple example

Sample-and-hold stages appear in front of analogue-to-digital converters, in multiplexed measurement systems and in peak capture. The drawing should show the control signal source and the hold capacitor, because the hold quality depends on it.

### What the drawings help you do

The element does not show droop rate, acquisition time or aperture delay. Those are device and component properties. Check the acquisition interval and hold duration against the measurement sequence and the selected component data.

### This particular reference

Analogue element marked S/H with a digital control input; it tracks the input, then holds the last value. An analogue switch alone passes signals; the S/H element includes the hold storage and buffering.

### Terms

- Signal: Electrical information passed between devices, rather than necessarily the main power supply.
- Schematic: A drawing showing function and connections rather than physical appearance.

Concept diagram: Identify the device and form → Read the connections and state → Check the equipment reference
A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram.

- [Overview of IEEE Standard 91-1984: explanation of logic symbols (SDYZ001A)](https://www.ti.com/lit/ml/sdyz001a/sdyz001a.pdf)
- [AN-1515: sample-and-hold function using an analogue switch](https://www.analog.com/en/resources/app-notes/an-1515.html)


## What it represents

The sample-and-hold element has an analogue input, an analogue output and a digital control input. While the control is in the sample state the output follows the input; when it changes to hold, the output keeps the last value. IEC-style analogue diagrams mark the digital control input with a # sign, as TI's overview describes for digital inputs on analogue symbols.
Sample-and-hold stages appear in front of analogue-to-digital converters, in multiplexed measurement systems and in peak capture. The drawing should show the control signal source and the hold capacitor, because the hold quality depends on it.
The element does not show droop rate, acquisition time or aperture delay. Those are device and component properties. Check the acquisition interval and hold duration against the measurement sequence and the selected component data.

## How to read it

- Identify the digital control input and its sense.
- Find the hold capacitor.

## Information to show or reference

- Mark the control input as digital.
- Show the hold capacitor value.
- State acquisition and hold timing where critical.

## Important distinction

An analogue switch alone passes signals; the S/H element includes the hold storage and buffering.

## Facts

- Inputs: Analogue signal plus digital control
- Key parameters: Acquisition time, droop
- Artwork scope: Original educational illustration; consult the applicable standard and the selected device documentation for the exact graphic

## Public references

- [Overview of IEEE Standard 91-1984: explanation of logic symbols (SDYZ001A)](https://www.ti.com/lit/ml/sdyz001a/sdyz001a.pdf) — Texas Instruments. Describes # as the marking for digital inputs on analogue symbols.
- [AN-1515: sample-and-hold function using an analogue switch](https://www.analog.com/en/resources/app-notes/an-1515.html) — Analog Devices. Manufacturer sample-and-hold application note.

## Graphic scope

Independent original educational concept illustration by Elora Grid. Not a certified standards graphic or manufacturer footprint. Unitless; not to scale. Original artwork licence: https://creativecommons.org/licenses/by/4.0/. Publisher material is linked only.