Hardware Implementation of Discrete time Systems
Many MCU implement the acquisition of the signal with a dual switch system.







simulate this circuit &ndash; Schematic created using CircuitLab

That is, the two switching elements are operated with a single signal, so as to have opposite conduction states.
While a state applies the signal to the capacitor, when the corresponding signal is activated, it stops applying the signal to the capacitor, and the voltage across the capacitor is available to be quantized.
The time during which the switch SW1 is closed, applying to capacitor signal is called the sample time or time of opening (\$t_s\$). The time during which the switch SW1 is open and SW2 is closed, is the time of quantization (\$t_q\$). Usually \$t_q\gg t_s\$