Discrete Op Amp

Once I was googling for discrete op amp ...

There is a lot of circuits on net. From standard API2520 to who knows what else. OK. I checked few of them with simulator and noticed that most of them will not work! Or could work conditionally. I will omit the details why, I'm sorry.

Recently I ended up the day with the idea to make my own discrete op amp. Nothing fancy, just stable amplifier with no pretencies. 70's style :)

Step 1:

I did it. Results:

Step 2:

1970 :)

Looks good to me

Step 3:

Well, I started with SPICE of course ... but I used what I have as transistors !

Step 4:

I have SR1 Audio Analyzer in my work. Here are some measurements:

Buffer G=1

THD+N = -106dB

Amplifier G=11 22k/2.2k

THD+N = -96dB

Noise = -122dB

Not bad at all !

Step 5:

Board is milled with this ... another story.

Enjoy.

:) fobi 05/03/2019

PS I intend to do dozen for my audio friends. Nothing commercial.