I like the theory, but don't think it's right.
Using it would give his transistor a gain of 1.5 at 10 amps. I know it is not the hottest transistor in town but it is not that bad. The data sheet states a gain of 5 minimum at 10 amps.
If you look at the 2N2222 which has a little better spec sheet the vbe Sat is speced at Ic=10XIb. And it only has an Hfe of 50 at 10ma.
yes,the transistor has different betas at different Ic, so this is why you divide the beta by 10, not the Ic. with a gain of 50, your rule would only pump 1mA into the base, and not guarantee saturation. My rule would pump 2mA into the base to guarantee it saturated.
It may not be your rule, but it's not my fault you weren't taught correctly. It's the way I was taught in the 70s.... particularly since different transistors have different gains at different Vce and Ic.... you up the gain factor by 10 to ensure saturation. Your method would be hit and miss, might work for most combinations of Vce and Ic, but not all.
Also, the correct beta for 10mA = 75 minimum (2n2222 or 2n2222a).
oh, by the way, we're not looking for Vbe saturation... we're looking for Vce saturation... Vce x Ic = power dissipated in the device, and we are looking to make sure Vce is minimum for a specific Ic to net lowest power consumption.
View attachment 69103