Hello.
When power transistors are used as switches, the base current can be significant, as the saturation beta may be as low as 10. On the other hand, the base _voltage_ need only be at Vbe(sat), and any additional voltage needs to be dropped by e.g. a resistor. Given the high currents, this voltage drop may be a significant loss.
This suggests to me that ideally the base of a low-side NPN switch would be powered by a low-voltage rail, only slightly higher than Vbe(sat). This way the conduction loss would be minimized.
Has such a rail been used with bipolar switches? If not, what's wrong with my thinking?
(Please don't tell me to use MOSFETs because they are better. I know that already. I'm looking for understanding, not solutions.)
Lauri