Discrete Op Amp

by fobi in Circuits > Audio

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Discrete Op Amp

d_fob_sim.JPG

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 :)

I did it. Results:

Downloads

Assy.pdf
Bottom.pdf
D_...fob_d1_brd.CKT.pdf

IMG-34e7e81a089a55ebd853c475cef198d3-V.jpg
IMG-938309fb7fefa98a1c347a6d1678380e-V.jpg

1970 :)

Looks good to me

d_fob_sim.JPG
d_fob_AC.JPG

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

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dfob_6gain11_1V.JPG
dfob_noise.JPG

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 !

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Board is milled with this ... another story.

Enjoy.

:) fobi 05/03/2019

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