Newbie question, please help! I just learned analog electronics and built a simple circuit using Multisim

电子发烧党

Newbie question, please help! I just learned analog electronics and built a simple circuit using Multisim [Copy link]

A simple common emitter amplifier circuit, why is the base current so small? According to the manual of 2N5551, shouldn't the voltage drop be only 0.7V? It stands to reason that the base current should be around 1A, right?

电子发烧党

Anyone? Help me with my job search...

btty038

Electronic Fever Party published on 2019-1-18 18:31 Is there anyone? Help me with my job search. . .

You need to calculate and adjust the value of the power supply

maychang

2N5551 is a low-power triode, and its package is TO-92. The maximum power is only about 0.6W. Its junction area is relatively small, so the body resistance of the junction is relatively large. The emitter junction voltage drop of 0.7V is for a base current of about 1 to 2mA. If the base current is large, in addition to the increase in the PN junction voltage drop, the voltage drop on the body resistance is also large, so the base current cannot be as large as the ampere level. In addition, the collector current cannot be as large as two amperes. If the collector current reaches two amperes, the voltage between the collector and emitter of the tube in the figure is about 10V, and the power dissipation reaches 20W. This tube would have smoked long ago.

maychang

"Shouldn't the voltage drop of 2N5551 be only 0.7V according to the manual?" Where does the manual say the voltage drop is 0.7V? Post it here and let's see. The manual does say that the voltage between the base and the emitter will reach 1V when the base current is 5mA.

maychang

The simulation software will not tell you that a component has been damaged by smoke, so simulation cannot completely replace experiments.

maychang

I also replied to a post between the 4th and 5th floors, saying that it needed to be reviewed, but three hours later, it had not been reviewed and released yet.