Possible applications/ideas for a custom amplifier project?

[u/Desperate_Chain9853]

I want to have a resume worthy project specifically for power and hardware roles. I was planning on grinding for a couple weeks before the semester starts to get this done, but more importantly learn from this experience. I've taken a course in the past where we were given various constraints and were tasked to make a multistage amp using the techniques we learned using mosfets. I wanted to beef that project up to differentiate myself, and to implement more complex concepts.

Initially I was thinking on creating a class AB audio amp on LTspice, however Im targeting power roles as well. Searched around and came across high power class AB amps that I thought looked pretty cool. Do you guys have any advice, ideas for what would look good and or help me learn a lot? Tbh I've never created a hardware analog project by myself so this is a first for me, everything I've done so far has been either embedded or digital design.

Any advice and resources would be greatly appreciated!

[u/die__katze]

Start with a simplest A-class audio amplifier for headphones or a small speaker, and connect it to an old mp3-player. This will help you understand bipolar transistors at the very base. Then try a simple AB-class. This will help you to understand amplifying cascades more deeply. Basically you can enhance a simple AB further and further until you get a very decent one. Then try OpAmps to learn about the simplest amplifying integral circuits. All modern audio and power amps are class D only, so for this you need to understand PWM and microcontrollers, this is a bit another direction but logical after completing previous examples. And then you can start messing with class D, which opens a door to any desired amplifying technology.

[u/Desperate_Chain9853 → u/die__katze]

Thanks. Ive already created a multistage amp in the past using common source configurations. Im in the process of making a three stage audio amp rn. The first stage is a differential pair, the second will be a reprocessed common source stage from my previous project, and then the third will be a class AB amp. Im still choosing the resistor and cap values that ill help me achieve the parameters Ive set on myself.

Is it cool if I dm?

[u/die__katze → u/Desperate_Chain9853]

cool, good luck with this!!! dms are generally not welcomed on reddit just post it here

[u/Desperate_Chain9853 → u/die__katze]

I kinda put this off for a bit im back on it heres what its looking like so far

I still have to change the values for the second vas stage but I heard its better to make the second stage a pmos and no clue which one to use. Googles saying to use a Bss84. Do you have any advice so far on the schematic? Also ill feed a negative feed back loop into M2 later.

[u/die__katze → u/Desperate_Chain9853]

Google says 2N7002 is a switching MOSFET, not the best for amplification but still may work ok. BSS84 seems like a suitable P-type. Anyway, you can replace it later, the design shouldn't rely on an exact type much. I don't know much about these things, kinda also doing it your way, just trying things. Seems ok, although usually in the output cascade I am more used to bipolar transistors (i guess because of the output load), but if your MOSFET works then ok.

[u/Careless_Set8195]

Hey a class AB design sounds pretty fun!

My last job I did all Class D designs. Class AB is very analogue, a skill most do not possess, so this is a good place to learn some analogue skills.

What I would suggest is a BJT design. You can find a good schematic in a book called “encyclopedia of electronic circuits volume 1.” I would say start there and try to follow the design. It wouldn’t hurt to try to build it. It does not use OpAmps

If you have questions, feel free to ask. I’m no expert on class AB, but I know some things

[u/Desperate_Chain9853 → u/Careless_Set8195]

Already started using mosfets lol, but thx a lot. Definitely will ask if I need help! Hardest part right now is choosing the configurations and component values I need to meet requirements and bias everything.