The triode is divided into PNP and NPN. There are three poles in total. The pin on the left side of the horizontal direction is the base B, and there is an arrow in the middle. One end is connected to the base, and the other end is connected to the emitter. electrode.
In the digital circuit, the switching characteristics of the triode are mainly used, and only the two states of cut-off and saturation are used. The formula: the arrow faces inward PNP, the conduction voltage passes along the arrow, the voltage conducts, and the current is controlled.
The key point is on the base and the emitter. Taking PNP as an example, when the voltage of the two deviates, that is, when Ve - Vb > 0.7v, EB is turned on.
Take PNP as an example, when Vb -Ve > 0.7v, BE is turned on.
Take the circuit of the actual project as an example:
This triode is a PNP type. When VE - VB > 0.7 v, EB is turned on, and the IC_ENABLE base is controlled by the microcontroller. When the IO pin is low, it is turned on between EB, otherwise it is EC In this project, IC_ENABLE is the enable pin of the CAN transceiver chip.
Therefore, the single-chip microcomputer controls this pin to be at a low level, and the EB is turned on. After the turn-on, it is at a high level, and the CAN transceiver chip is successfully enabled.