The value for C1 was 100nF. According to the datasheet [1], the range of capacitance for these instabilities to occur is 10nF to 100nF – the same range covered here. Figure 5 Simulated outputs of the ...

The TL431’s datasheet is full of cool applications, and the combined functions of a voltage reference and comparator-driven transistor in a couple-cent piece of silicon make that work.

[Ken Shirriff] had to get down into a bit of semiconductor physics to give us an explanation of the TL431, which he calls “the most common chip you’ve never heard of”. [Ken] may w… ...

The design issue in this case, comes from the TL431 data-sheet: You must inject more than a 1-mA biasing current to benefit from different guaranteed specs among which is the TL431 gain.

The version of Multisim Spice offered by Analog Devices here does not include a device model for the TL431 group of voltage regulators, so when I needed one, I made one. Going for the super-simple and ...