Lots of electronics books lay out circuit diagrams but don't really explain what each individual component does. Here this is detailed where the purpose of each component is thoroughly explained. Super helpful.
Absolutely simple way to explain the functioning of electronic ccts. This gentleman has a knack for explaining electronics very well and he is very knowledgeable.
13:00 - Should not a right end of a capacitor be connected between diodes? In your scheme its connected below both diodes. Let's say positive signal comes in. Current won't flow up - bottom diode blocks it. It also won't open PNP transistor. it can only go down trough resistor to -10v and this does nothing useful. After plugging these diodes you should show how current flows from input and which way to output. Marking voltages is not enough to me to not have doubts. Maybe your sheme is correct, but then I do not understand what happens at PNP base node. How input signal voltage influence potential at that node?
this is very intetresting! Finally something not too easy for my projects :) I am using those kinds of amplifier (I have circutis from books etc.) but it is always better to have more understanding how they exactly work so I can design them better :) I have built recently my AM radio for 225 kHz from scratch and need to improve my amplifier to have better sound quality.
Yes Bob, but if the diodes are not properly matched to the BE junctions of the transistors and have the same thermal characteristics you risk thermal runaway. However, you can use the same spec transistors as the diodes. That way you can get sufficiently close matching easily and without the effort of selecting the right diodes.
I plan to build a 1959 DDR retro radio using transformers and germanium transistors and the old schematic. I really like this old technology of drive two transistors through two transformers. Sounds strange, but it's just a learning project. ;) BTW: Great content, thank you very much Professor!! By far the better way to learn electronics is to first get a general understanding of what actually happens and then practice the math. I really missed this approach during my time as a student. In the lecture my prof couldn't say what the essence of a Fourier transformation is. ;)
Thanks! Great explaining video,even for a slow learning hobby beginner. I have been struggling with npn pnp and the basics a long time to get it in my head.
I have seen this in a lab-book!They used a pair of (2N3904 ,2N3906) transistors',and two (1N914) diodes'. I hope you will cover the subject of speaker 'impedance-matching' to this amp in the future!Thanks' for a great video/class!
I'm going to make a followup video with a better trick I forgot to add. Feed the bases of the transistors with an op-amp and feed the final output back to the inverting input with an appropriate voltage divider.
@@uni-byte You do realize that Bob is trying to teach electronics and when you are trying to learn the concepts there is something call information overload. And I think that he has a full grasp of subject matter.
Can you do a follow-up video and explain what happens to ac signal going through the diodes? I can't wrap my mind around how the sound gets to bases of the output pair. Thanks, you are the best!
hi sir, you are a great teacher for me. I always refer your videos for understanding circuits .can Make video on all (a,b,c and ab) class amplifiers and network theorems pls pls pls😅.
7:39 one question, of there are no resistors, only transformers I am always worried about too much current going into the base of those transistors. How is that possible that they are not overloaded with current. I mean I understand how transformers work but still there is quite a lot of current going int othe base right?
In the class B transformer design there was ONE resistor in series with the transformer center tap. This sets the max base current along with the dc resistance of the primary windings.
Aaa yes. I forgot that there was a resistor there too but I think I have seen somewhere a class B amplifier without any resistor there, it was a chinese radio kit...
I was watching a video about vacuum tube amplifiers and the person covered class B amplifiers. He showed a graph of voltage vs. current and how class B amplifiers operate starting from the cut off region: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-o6NX3MiJL6k.htmlsi=bmL0bTFQ63el4txC&t=28m48s So looking at the voltage vs. current graph class B amplifiers operate partially in the non linear region meaning they introduce distortion beyond just the cross over distortion. So, wouldn't something similar occur with transistor based class B amplifiers?
Very brilliant design. The situation is well balanced and both NPN and PNP transistors are open situation, when a negative wave comes into, it get -10V power's its side and push up through the diode's kathode side to the next kathode and this make +0.7V balance distort , for example, get +0.5V and NPN transitor needs minimum +0.7V so NPN transistor closed. When a +0.2V positive wave comes into the system, it reduces well balanced -0.7V to -0.5V so PNP transistor's breaking point needs -0.7V and PNP transistor closed. If my interpretation is wrong, please make it clear. Thanks.
The voltage difference between the base of a transistor and the emitter is "0.7V". This causes x-over distortion. The voltage difference between the terminals of a diode is also "0.7V". So this is used to negate the voltage difference between the base and emitter of the transistor, which should then "eliminate" the x-over distortion. But b/c we have 2 transistors we need to have 2 diodes to negate both.
