# Glossary

This tutorial introduced a lot of terms, so here's a recap in case you need to refresh your memory on one:

## 1LSB:

One Least-Significant Bit:  The smallest change of input voltage that will make an ADC's ouput change from one code to another, or the smallest voltage an ADC can measure repeatably.

Analog-to-Digital Converter:  A circuit whose output consists of digital patterns called codes.  Each code corresponds to a specific input voltage.

## Aperture:

The time when a sample-and-hold circuit is connected to the input.

## ASR:

Aperture Slew Rate: The fastest a signal can change and still be measured accurately by an ADC.

## Calibration:

Comparing a measurement to a better one, or measuring a known signal, to find a circuit's error.

## Code:

A pattern of ones and zeros.  In this case, a code is the output produced by an ADC.

## Compensation:

Subtracting a known error from a measurement without actually correcting the circuit to remove the error.

## Correction:

Modifying a circuit to remove a repeatable error.

## Correlation:

A relationship between the error and the signal being measured.

## Distortion:

Error that changes depending on the size of the input signal.

## Dynamic signals:

Signals that change at least 1LSB during an ADC's sampling interval.

## Error:

The difference between the actual input voltage and the voltage represented by the ADC's output code.

## Gaussian distribution:

A common kind of random signal with convenient statistical properties.

## Input-referred error:

The signal you'd have to add to a perfect ADC's input to make it produce the same output as a real ADC.

## NFCR:

Noise-Free Code Resolution: The amount of useful information you can get from an ADC in a given set of operating conditions.

## Noise:

For the purposes of this tutorial, noise is random error that can't be corrected or compensated.

## Offset:

A DC voltage added to another signal.

## Repeatability:

The ability to reproduce a condition on demand.. the main difference between ideal circuits/signals and real ones.

## RMS:

Root-mean-square:  A way to measure AC signals that lets us compare them to DC measurements.

## S&H:

Sample and Hold: The input circuit for most ADCs.  It captures the input quickly, then holds that voltage stable while the ADC generates an output code.

## Sample rate:

The number of different codes an ADC can produce in one second.

## Sampling interval:

The time it takes an ADC to generate a code.

## SAR:

Successive Approximation Register: an ADC architecture that compares the input to its last guess several times, reducing the error with each new guess.

## Sigma-Delta:

An ADC architecture that uses positive and negative pulses of known charge to make a capacitor's voltage equal the input voltage.

## Slew rate:

The amount a signal's voltage changes over time.

## Standard deviation:

The band of values around a signal's average that contains 68% of the readings.

## Static signals:

Signals that stay at a fixed voltage, or change less than 1LSB during an ADC's sampling interval.

This guide was first published on May 23, 2019. It was last updated on May 23, 2019. This page (Glossary) was last updated on Nov 11, 2019.