Real transistor operation

I am just a person beginning in electronics on my own . I have been reading how transistors work. All explanations seem to talk about hole flow. But holes don’t really move. Can anyone explain what really happens in an NPN and a PNP transistor? I am thinking that there are two levels of electrons moving. Those that are free in the conduction band and hole movement really being electing movement in the valence band. If someone could explain both but especially PNPs that would be so great. Diagrams much appreciated.

by Kriskan
January 05, 2019

1 Answer

Answer by frequencydrive

This is not the answer to your question but just some advice. I just finished my electrical engineering degree. I took electronics and all that discussion about hole flow or electron flow will not help you design a circuit. It is great to know if you are interested in semiconductor physics, but unnecessary knowledge at this point in your electronics adventure. I never needed to know what the electronics were doing in the valence bands in order to design an amplifier using a BJT. You can get too far down in the weeds trying to account for electron behavior at this point. Just start with how to turn on the transistor and the basic operation in the three regions of operation such as saturation, cuttoff and active. For now just skip the "conduction band and hole movement". The good stuff is the three regions of operation that is where all the work is done.

+2 votes
by frequencydrive
January 17, 2019

Dear Frequencydrive and Mike, Thanks for taking the time to answer me. I understand what you are saying and have heard that response before.

I am only interested in this idea at a low level . I was try to picture in my mind how they work. There are a few YouTube videos that show pictorially how electrons leave the emitter flow through the base and are drawn toward the collector in an npn transistor. I was try to imagine what happens in a PNP transistor. They say just imagine the holes doing the flowing in a PNP. It may be silly but once I knew holes don’t really move that idea didn’t work for me. Thanks again for your help.

by Kriskan
January 18, 2019

Sorry to be pedantic but I can't let you get away with saying that. In P-type materials it is undoubtedly the holes that move. I don't know your age or level of education, but in fifty years since gaining my degree I never heard such heresy from any source, and I have worked alongside a great many electronic and process engineers. I also have gained many patents in electronics and have lectured and written technical articles. You are very much in a minority of one. What you do not understand is not necessarily silly, it is just a flaw in your education.

by mikerogerswsm
January 18, 2019

Dear Mike

Actually I have no particular education. I am an old woman 61 that is just interested in transistors. I got the idea that holes do not actually move from an old textbook I found by Ronald Tocci. In it he said they talk about holes moving but it is actually electrons moving that make it appear that holes move in the opposite direction. I appreciate your post. As I have no real education I am trying to learn on my own . Therefore, I have many misconceptions.Thanks again.

by Kriskan
January 24, 2019

by mikerogerswsm
January 24, 2019

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