200W BJT SFA (BJT mod from Dadod 100W CFA with Input Stage active load)

[printnik]

Hi guys. My Development Team Improved Dadods 100W CFA with Input Stage active load (current mirrors) and even lower distortion -100W:
https://www.diyaudio.com/community/threads/200w-mosfet-cfa-amp.243481/post-4857977
The amplifier turned out with very low distortion. Nice clipping. Little delay. Protection.

 

[dkfan9]

What is SFA?

 

[andrewlebon]

Hello Printnik
greetings can you explain more about the protection
circuit part is it short circuit with latching relay
warm regards
Andrew

 

[printnik]

Andrew, the relay will not have time to protect the transistors. This circuit uses a fast trigger protection. The relay can be used for standard DC voltage output protection. Relay contacts must be covered by feedback. It is necessary to connect a high-resistance resistor in parallel with the relay contacts in order not to break the DC feedback.

 

[printnik]

Correct connection.

 

[printnik]

I corrected the diagram.

 

[de Ocampo]

Hi,
Out of curiosity, what do you mean by 'improved' would you care to differentiate the changes made vs Damirs design?
Thanks!

Albert

 

[printnik]

Hello de Ocampo. I showed the improvement in the diagram. 6.8 ohm resistors degrade thermal stability. Input transistors collector voltage-base equal to zero will not work normally.

 

[overall feedback]

It is BJT and it will work. Until CE voltage cca 0.2V.

 

[dadod]

Hello de Ocampo. I showed the improvement in the diagram. 6.8 ohm resistors degrade thermal stability. Input transistors collector voltage-base equal to zero will not work normally.

I missed this thread.
I will not call it improvement, as overall feedback says transistor works with very low CE voltage. You used cascoded VAS, I tried it bat not need here where distortion is so low and it eats headroom. Different compensation, way?