If you are driving the transistor’s base with 0V to 5V while emitter is on 12V (Vbe is then -7V to -12V), you can’t fully turn the transistor off as there is some base current flowing at all ...

Field-effect transistors fabricated from carbon nanotubes have been investigated extensively over the past two decades. This study demonstrates a nanotube-based integrated circuit design that ...

This made me look at the turn-off specs for the npn (a 2N2222A) and, for the first time I can remember, I noticed that the turn-off test circuit in the data sheet used a negative drive to the base.