Question about BJT

[cmark01]

Hi all,

I am studying BJT now, and I have some questions.
If I have a BJT with common emitter connection, is the connection as condition 2 possible? What will happen if I connect a BJT like condition 2?

In condition 1, I know the BJT is saturated. When it's saturated, does it means all electrons and holes are recombined in base due to large amount of holes provided fom current going into base?

Thank you

 

[crutschow]

Condition 2 will cause the transistor to cease to exist as a transistor. The base emitter-junction of a BJT looks like a diode and the current it conducts is limited only by it's internal resistance, which is low. To properly bias a bipolar transistor you must have a resistor in series with the base to limit the current.

My memory is a little hazy on the subject, but I believe your description of BJT saturation is correct.

 

[colin55]

Basically the base of a common transistor cannot be higher than the emitter by more than 0.7v - 0.9v If it is say, 1.1v, you know the transistor is completely damaged. Although some Japanese transistors have a base-to-emitter voltage as high as 1.5v when in the fully saturated mode.

 

[cmark01]

thanks a lot!!

 

[audioguru]

Power transistors have high base-emitter voltages at high currents. The max base-emitter voltage for a 2N3055 transistor wirh a collector current of only 4A is 1.5V and is higher at higher currents.