Rail to Rail MOSFET Buffer with Error Correction

[m0rten]

The additional filtering was to isolate the input stage from big current bursts in the OPS.
But I'm no expert! 😎

 

[lineup]

It is a good buffer.
I tested with a good opamp as input and I let the output be 10Vp.
At 1kHz THD was 0.0003% ... that is -110dB.

 

[jxdking]

Optimized the resistors' value around the bias network.
Added degenerative resistors R29, R32 to Q5, Q6. This solves the transient current spikes. It also limits the current of Q7 and Q8.

Bode plot

 

[m0rten]

Hi again!

Spent some time with layout... first one unsuccessful, but here is a finished board.

Latest schematic for this PCB:

PCB:

 

[jxdking]

Thanks @m0rten

I am working on my own version. I have to come up my own PCB layout as I want to adapt to existing mounting holes.

PS: C311/C312 are ceramic caps. 0.22 Ohm resistors are 2W, all other resistors are 1/4W.

 

[m0rten]

C311/C312... 10uF ceramic caps? Sounds expensive!

 

[jxdking]

C311/C312... 10uF ceramic caps? Sounds expensive!

I bought some 10uF ceramic caps before, primary for audio input coupling.
I realize the voltage here is pretty low. They are perfect here.

The price before tariffs. The 16V version.

The 50V version is about double the price. The 16V version is enough here.

 

[m0rten]

Nice!

 

[m0rten]

I bought some 10uF ceramic caps before, primary for audio input coupling.
I realize the voltage here is pretty low. They are perfect here.

The price before tariffs. The 16V version.
View attachment 1455637
The 50V version is about double the price. The 16V version is enough here.

Do you expect more changes to you design? I am eager to make gerbers...

 

[jxdking]

Do you expect more changes to you design? I am eager to make gerbers...

I think that's it.
I will put my PCB order this weekend.

 

[m0rten]

Good luck! I just ordered mine!
Some time we may compare notes...

😎 morten