Published on: 2023-01-27
Written by Nathan Pulver
I do not have the knowledge to tell you what a transistor is and how to use them. I am writing this article because I have tried using transistors in some electronics circuits and struggled every time. This is going to be a series of articles that summarize my findings each time I spend some time trying to learn some more about them. I will probably get some stuff wrong and misunderstand. If you want to learn with me, follow along and hopefully I do not misguide anyone.
Keeping it simple
Alright, I have a whole box of transistors I got from Aliexpress and I don’t want to try to understand all of them. I know there are loads of transistor types but I am going to keep it simple and focus, for now, on a BC548 NPN BJT. What the fuck does NPN and BJT mean? NPN is the orientation of the doped semiconductors in the transistor and BJT means Bipolar Junction Transistor. I don’t think it is important to go into detail into either of these for now. I just want to use the thing.
Collector, Base and Emitter
On our BCN548 transistor that we are focusing on, looking at the flat face and reading from left to right, pin 1 is the collector, pin 2 the base and pin 3 the emitter. I think that the base is always the middle pin on all transistors, but I am not 100% positive. After looking at many websites, I think the best explanation I saw was that the collector is our large electrical supply while the base is used to control the current of the large electrical supply and the emitter is the output of the controlled large electrical supply. So, current flows from collector to the emitter, but the amount that flows is controlled by the base.
Applying power at the base of our BCN548 transistor allows current through. I think the importance of the previous statement is that some transistors allow current from collector to emitter when there is no current. Again not completely sure, but I saw this emphasized and that seems like a logical progression to me.
Questions to answer for the next post
This is all I have time to go through right now but there is much much more to learn. Next time I want to figure out how to use these as an amplifier. I think I could reason it out from just the above information, but I am not really sure on the wiring for the base. Does the signal generator at the base, say a microphone, need to be connected to the same power supply/ have the same ground as the BCN548? What is the range of voltages I can apply across the transistor? What is the max current it can take? Hopefully we can figure all of that out next time and get a working circuit.