TL431: Dears ，In the TL431 datesheet ,How the graph Figure SMALL-SIGNAL VOLTAGE AMPLIFICATION VS FREQUENCY be measure ? could you offer the schematic and computational formula? many thanks~

Hi Andrew,

This is a very old graph so I am unsure on the tools that where used to originally measure this. Today there are many ways to measure the gain and phase. There are two approaches I would use.

1. Use a frequency analyzer such. The following is a good app note which discusses this www.ti.com/.../slup386.pdf . Here i a good video discussing this training.ti.com/engineer-it-how-test-power-supplies-measuring-stability

2. Use a network analyzer. The following is an app note that discusses this www.ti.com/.../snva364a.pdf

There should be no equations involved for this. This is just an AC measurement that is created by injecting a AC signal on the feedback loop and measuring the response on a frequency or network analyzer.

-Marcoo