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Hello everyone, in this lesson we will learn the conduction conditions of the triode

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Transistors are used as switches in PC circuits

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When used as a switch, there are two working states, one is on and the other is off.

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Then there must be a pin to control it on or off

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This pin is the B pole

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The B pole of the PNP transistor is connected to the N area

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N is negative and means low

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Then when B pole is low, it conforms to its internal logic

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When B pole is high, it does not conform to its internal logic

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Therefore, the PNP transistor is turned on at low level and cut off at high level.

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Let's look at the NPN transistor

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The B pole of the NPN transistor is also the control pole, which is connected to the P area.

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P is positive, which means high

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Then the NPN type transistor is turned on at a high level and cut off at a low level.

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So how high or low must the high and low levels be to turn on?

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Generally, we compare pole B and pole E

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Let's remove the C pole first, and we can see that a diode is formed between BE

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I believe everyone is familiar with the conduction conditions of the diode.

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The positive electrode is more than 0.7 volts higher than the negative electrode, and it can be turned on.

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The turn-on voltage of the triode is also 0.7 volts

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Then we get the conduction condition of the triode

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The NPN transistor is turned on when the level is high

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That is, when the B pole is 0.7 volts or more than the E pole, BE is turned on, and CE is also turned on.

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The PNP transistor is turned on when it is low

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That is, when pole B is 0.7 volts or more less than pole E, EB is turned on, and EC is also turned on.

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EB is turned on, and EC is also turned on.