I don't understand. Below is not intended to be a wise-acre but to illustrate my confusion.
So one should start with a given base current then find a load that needs 10X the base current?

 

He could have avoided any confusion by simply putting a notation on the schematic. That's what I'd do.

It wasn't until years later that I saw the symbol that indicated the internal resistor. Maybe they had not invented it yet and nobody, at least at that company, thought it a problem.

 

The 2n3904 datasheet is here: https://www.onsemi.com/pub/Collateral/2N3903-D.PDF

A few things, The absolute maximum ratings. You probably want to run at least 1/2 of those. There''s the case and basing diagrams.
thermal resistances allow you to size heatsinks.

let's just pick one:

Collector−Emitter Breakdown Voltage (Note 2)
(IC= 1.0 mAdc, IB = 0(BR) VCEO 40 Max(−) Vdc

The VCEO means Collector to Emitter, base Open. Ib=0 confirms this. IC was the collector current operating condition the measurement was taken. damage will occur if the C-E voltage exceeds 40.

This datatsheet is broken down into the DC and small signal characteristics. Note that Hfe Varies. Hfe is the current gain. It always is all over the map. You yep Ic = Hfe*Ib; one of the simple relationships. Also Ie=Ib+Ic is another relationship.

You have Vce(sat) and Vbe(sat) where sat means saturation. If we don't know we pick 0.6 or 0.7 V. Those number vary with temperature. About -10 mV/deg C for silicon. I think it's negative. So a transistor can be used as a temperature sensor.

When you use a transistor as a switch, you want it saturated or the lowest it can go, There is always going to be a B-E diode and a C-E diode.
Those drops are losses. So when you size base resistors, you have to incorporate that drop. e.g. Rb = (3.3-.3)/10e-3

Not every resistor is available. The set really cares about resistance ratios. There are tolerances everywhere.

Next we have small signal characteristics which isn't applicable to the transistor application as a switch.

I do want to introduce because it's relevant, the concept of a digital transistor. See https://www.rohm.com/products/faq-search/faqId/234

I want to make a comment about LEDs. When leds came out 10 mA was a typical current and 2.1 V a typical voltage drop. That;s not true anymore. The drop Vf will track intensity variation. The actual amount of the drop depends on the color of the LED. You can have LEDS with a typical operating current of 1 mA.

12 V, 5V and 24 V LEDS have internal resistors.

The reverse voltage on a typical LED is about 6V. When you have two back to back, the LED will respond to AC an done will limit the other, but you still need a series resistor.

Don;t operate LEDs in parallel. You can operate them in series with one resistor. Again the variation of Vf may change the relative intensities.

LED's are 'current devices". You intentionally vary the current to change the brightness.

 

I don't understand.

Base current = 0.1 x collector current, not 10 x.

 

Er ... no. Vice versa.

Base current = 0.1 x collector current, not 10 x.

Thank you for correcting me and clearing up my confusion