Well, if it's not an advertised spec on the datasheet, and constrained in the direction you're using it, then all guarantees are off and it's on you to qualify the parts on a batch-by-batch basis.

I think that counts as "cursed" from a design-for-manufacturing perspective.

"After a production run of 12,000 units the TR-808 was no more." https://secretlifeofsynthesizers.com/the-strange-heart-of-th...

> the usual garbage undergrad textbooks

Out of interest, please could you give some examples of textbooks you consider garbage, and some you consider not to be (undergrad or otherwise)?

This is amazing. Now I'm even more upset he scored so low on Eurovision.

The man is a treasure

No. That capacitor would charge at a few volts, i.e. the sum between the voltage on a conducting LED and the voltage on a conducting silicon diode (the base-collector junction).

So the capacitor would initially divert a part of the discharge current from the LED, but later it would discharge itself through the LED. So it might make the current impulse through the LED smaller and wider. Such a capacitor would increase the probability that the transistor would be damaged by the periodic breakdowns, by extracting a big current pulse through the base. Depending on the transistor structure, a capacitor on the base could also stop the oscillations, because the current extracted through the base could eliminate the negative resistance that appears on the voltage-current characteristic in the breakdown region when the base is not connected or it is connected somewhere only through a big resistor.

The frequency is very easily adjustable without changing the schematics, by changing the value of the resistor that charges the capacitor, before the breakdown voltage is reached, or by changing the value of the capacitor.

The RC product determines the charging time, which constitutes most of the period of the pulses.

While the breakdown voltage of the base-collector junction varies wildly even between transistors of the same type, the breakdown voltage of the base-emitter junction varies very little between planar-epitaxial transistors, because in all such transistors the emitter has the maximum possible doping, which is limited by the solubility in silicon, and the base must also be much more strongly doped than the collector, but much less doped than the emitter, which limits the range of possible dopings. Because in this case the breakdown voltage of the base-emitter junction is determined mainly by the doping of the base, there is little variance between transistor types and between manufacturers.

Typical breakdown voltages for base-emitter junctions are e.g. around 10 volt, while the manufacturers specify breakdown voltages like 7 volt, to have a safety margin.

It's one of those characteristics you can't rely on unless you select / bin parts. Also depends on temperature. Which is why no one does this in a production design - it's expensive and unreliable.