Sampling Dac

Sampling Dac

DAC : What is "sample and hold" and "interpolation between samples"?

Compare schemes which use:
(i) Sample and hold.
(ii) Interpolation between samples.

[12 marks]

DAC is an abbreviation of Digital-to-Analog Converter.
ADC is an abbreviation of Analog-to-Digital Converter.

Normally, "sample and hold" is a ADC term, in which an analog signal is "sampled" by charging a capacitor to to voltage of the signal, and then "held", by disconnecting the charge circuitry and giving the convertor stage some time to digitize the (now constant) held sample.

In terms of DACs. You can output a sampled waveform by writting each (digital) sample to the DAC at a fixed interval. I guess this would be your "sample and hold" DAC. If the DAC has a fast settling time relative to the frequency that you write to it, this method will produce a "staircase" form of output.

In the case where the DAC settling time is fast, sometimes it can be filtered digitally by computing (interpolating) one or more points between each sample pair and outputing them at a rate faster than the "sample and hold" case. The waveform will then appear to be comprised of a series of ramps rather than steps. So it will appear "smoother" (more continuous).