Transistors

[Mark Hennessy]

The base voltage is just a regular voltage divider and it's 3 volts so I won't dwell on that.
Below I figured you are meant to multiply 10K by 30 K and then divide that figure into 40 K (the sum of the 10 and 30). That gives the 7500 cited below.

This part is Thévenin in action. In other words, replace that potential divider with a 3V voltage source and a 7k5 resistance.

I've mentioned this before - if you haven't already (and I'm guessing you haven't because you didn't spot it here) - please make the effort to learn it. It is far more fundamental than all this transistor stuff, and actually far more useful.

I won't say what I think of that tutorial because this is a family-friendly site. Similar comments apply to just about every other article I've read on there. Unfortunately, because it's quite well presented and search-engine friendly, a lot of beginners cite pages from that site when really they shouldn't.

You didn't reply to my post recommending text books a few days back. I thought that was a bit rude, though hopefully it was just an oversight. There is a lot of badly-written stuff out there, and you're not yet able to tell that apart from the good stuff - but that's where we can help. You don't have to follow just one method, as you said, but at least stop following the bad ones. I've lost count of the number of times I've recommended other books, only to see post after post talking about ARRL and other poor references. Please respect our experience here - or at least make it clearer to us that you respect our experience - or I'll have to question how things continue. We have been extremely patient and tolerant here.