# Track vs sample-and-hold

This is the output of both track-and-hold and sample-and-hold.

But when I searched for its circuit I am getting the circuit I have shown below for both.

So my question is: if the circuit for sample-and-hold and track-and-hold are the same then how is the difference between the two getting reflected in the circuit? Is the control signal input different for both, and if it is, then how is it different?

• You can guess it's the same thing as they even managed to confuse their wording in the graphic itself. The (b) graphic says "Sample mode" and "Hold mode" and not track and hold. I'm not sure that graphic is all that helpful (at least on its own). I'd say to show the difference between an ideal and real circuit you should try to hold the value at the same points of time and indicate that you get a lag (because of needed sample time) in a real circuit and thus maybe not the value you'd expect. Commented Jun 22, 2017 at 15:36
• A track & hold is typically used for deglitching a DAC, where as a sample/hold is used on the input to an ADC Commented Jun 22, 2017 at 18:27
• The first image is basically the second with an infinitely short sampling period. Commented Jun 22, 2017 at 20:26
• Take a look at this: youtube.com/watch?v=KvjiKzBaTAs Commented Sep 22, 2018 at 19:03

There is no difference. The two terms are used interchangeably:

## Track-and-Hold

Track-and-hold, often called 'sample-and-hold,' refers to the input-sampling circuitry of an ADC. The most basic representation of a track-and-hold input is an analog switch and a capacitor. (See figure.) The circuit is in 'track' mode when the switch is closed. When the switch opens, the last instantaneous value of the input is held on the sampling capacitor, and the circuit is in 'hold' mode.