Sample and hold

The sample-and-hold circuit is composed of analog switches, storage elements and buffer amplifier A. At the sampling moment, the digital signal added to the analog switch is low level. At this time, the analog switch is turned on, so that the voltage UB across the storage element (usually a capacitor) changes with the sampled signal UA. When the sampling interval expires, D becomes a high level, the analog switch is disconnected, and UB remains unchanged at the moment of disconnection. The function of the buffer amplifier is to amplify the sampled signal. There are two basic types of connections in the circuit: one is to amplify the signal before storage, and the other is to store and then amplify. For an ideal sample-and-hold circuit, it is required that the switch has no offset and can move quickly with the control signal, and the impedance of the disconnection should be infinite. At the same time, it is also required that the voltage of the storage element can track the voltage of the analog signal without delay, and can be at any length Keep the value unchanged for the period of time