The triode is one of the commonly used components in the electronics industry. It is a current-mode control device. It has three working states: cut-off region, amplification region, and saturation region. When the triode is used as a switch, it works in the saturation region. The following briefly explains the method of using the triode as a switch, and only talks about dry goods.
NPN type triode
Taking driving buzzer as an example, the circuit of NPN driving buzzer is shown in the following figure:
The output port of the single-chip microcomputer is connected to the base electrode through a resistor, the emitter electrode is connected to the positive electrode of the buzzer, and the collector electrode is connected to the power supply through the resistor. When the pin SPEAK of the single-chip microcomputer is at a high level, the PN junction is forward biased, the triode is in a conducting state, and the two pins of the buzzer are energized and sound.
Remember: NPN transistors conduct when their bases are high.
PNP type triode
The output port of the single-chip microcomputer is connected to the base through a resistor, the collector is connected to the positive electrode of the buzzer, and the emitter is connected to the power supply through the resistor. When the pin SPEAK of the single-chip microcomputer is low level, the PN junction is forward biased, the transistor is in a conducting state, and the two pins of the buzzer are energized and sound.
Remember: the base of the PNP transistor is low when the transistor conducts.
Although today's article is very simple, it is very practical. The textbooks have always talked about triodes theoretically but not practical. I hope this article can help you.
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