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I am a novice interested in learning amplifier design for audio projects. I can design simple "elementary" amplifiers such as CE, CB, and CC and can make them work with desired impedances, good biasing, and properly-sized coupling capacitors. I am good with basics like Ohms Law, KVL/KCL, and can do simple analysis of discrete bjt circuits. I have probably a basic understanding of transistor models like hybrid-pi. I'd like to get to the point where I can design more useful circuits with multiple stages that would actually work to drive real-life speakers, but have struggled to find a good source. I don't know what I'm missing, but when I look online for information on combining stages, power amplifiers, class AB amplifiers and the like it's clear that there are gaps in my knowledge. What is the next thing I need to learn about? And, perhaps more importantly, can you suggest a book that might meet me at my level?

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    \$\begingroup\$ Your question will be closed soon, so before that happens, have a look at JohnAudioTech's channel on youtube and the series of videos he did on his audio amplifier. Does not require any more prerequisited than what you've listed. You need to learn about current mirros, active loads, feedback... The books by Self and Cordell might help you. \$\endgroup\$ – Sredni Vashtar Sep 25 '20 at 23:14
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    \$\begingroup\$ I had in mind two Douglas Self books: "Small Signal Audio Design" and "Audio Power Amplifier Design", while Cordell has written "Designing Audio Power Amplifers". I assumed you were interested in audio applications. \$\endgroup\$ – Sredni Vashtar Sep 26 '20 at 0:45
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    \$\begingroup\$ It would be closed because it is opinion based, too general, and includes a product recommendation. That said, you may find long-tailed differential pairs useful. They are what makes op-amps what they are. Also cascode might be useful. \$\endgroup\$ – DKNguyen Sep 26 '20 at 1:04
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    \$\begingroup\$ @mkeith I think Douglas Self and also Cordell are both worth a thorough read. However, that said, there is a certain assumption about prior knowledge by both authors. They are talking to other well-informed readers and covering a lot of those thoughts others might wonder about. But that means its less for those who are trying to work lift themselves by their own bootstraps and struggling to understand each section within the amplifier design. It's kind of assumed that you have the basics down and want to work on the important details for a real product. \$\endgroup\$ – jonk Sep 26 '20 at 4:43
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    \$\begingroup\$ I read Self after I got my BSEE. You may well be correct. Nonetheless, when one reads an advanced text and doesn't fully understand it, at least it gives one an idea about the concepts one needs to study. \$\endgroup\$ – mkeith Sep 26 '20 at 6:28
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I suggest you examine the various functions of this circuit (question asked today)

Output Stage Clipping

where

  • diffpairs are the input (PNPs) with current source

  • differential_to_single_ended converter

  • rail_to_rail gain stage

  • biasing, which is ttemperature-compensated

  • output devices that need debugging

with problems

  • greatly imbalanced source resistances into bases of the diffpairs; left transistor has 10Kohm; right transistor has (the global feedback network) 2K || 20K; these imbalances cause output DC offset voltage that will injure the loudspeaker load

  • no frequency compensation, so probably the amplifier will oscillate

  • no ZOBEL network (series R+C) on output, to help stabilize the amplifier

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I'd suggest Field Effect Transistors as your next field of study. There are several different types and you will find widespread applications.

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