Sample and hold

Sample and hold circuits and related peak detectors are the elementary analog memory devices.

For practically all commercial liquid crystal active matrix displays based on TN, IPS or VA electro-optic LC cells (excluding bi-stable phenomena), each pixel represents a small capacitor, which has to be periodically charged to a level corresponding to the greyscale value (contrast) desired for a picture element.

In order to maintain the level during a scanning cycle (frame period), an additional electric capacitor is attached in parallel to each LC pixel to better hold the voltage.

[4][5] Sample and hold circuits are also frequently found on synthesizers, either as a discrete module or as an integral component.

They are used to take periodic samples of an incoming signal, typically as a source of modulation for other components of the synthesizer.

A simplified sample and hold circuit diagram. AI is an analog input, AO — an analog output, C — a control signal.
Sample times.
Sample and hold.
A sample-and-hold integrated circuit ( Tesla MAC198)
The sample and hold stencil on a Korg ARP Odyssey synthesizer.