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		olliej on April 21, 2020 \| parent \| context \| favorite \| on: Reverse-engineering the TL431: the most common chi... Follow up dumb question - I thought transistors take time to charge/discharge/do-physics-things, how do they avoid resistance changing over time.

SAI_Peregrinus on April 21, 2020 [–]

They change a bit, but primarily at startup. After that they're controlled by the stability of the biasing.

I'd recommend "Designing Analog Chips" by Hans Camenzind[0], the designer of the 555 timer. Particularly chapter 3, "Current Mirrors".

[0] http://www.designinganalogchips.com/ has a free pdf

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