Getting late right now. I’ll check this again in the morning.
Regards,
Dan
The drain Label is incorrect.
I was using the word “drain” to identify pin 3 of J4, nothing to do with the FET.
The connection: Pin 2 of the FET to Pin 1 of J4 is correct.
The problem is because you are mounting the FET under the PCB with the pins bending up, pins 1 & 3 of the FET footprint need swapping.
If you leave the board as it is, you will have to mount the FET with the top facing down which won’t disperse the heat.
It’s a bit off topic, but the fet + resistor is a circuit type used for jfets, but the 6N50 is apparently an enhancement type MOS fet and then that circuit does not work at all.
Edit: HMK (below) posted a link to another datasheet, and that is a depletion mode MOS fet.
I recommend you build this thing on a breadboard or perf board first before you design a PCB around it.
1 Like
What a PITA trying to figure out TAB UP and TAB DOWN!
YES!!! 
Edit: the "yes’ is reference to “I think I got it” not “a PITA”. 
The datasheet below actually states depletion type, see also the diagrams of Gate voltage to drain current on page 3.
https://www.mouser.se/datasheet/2/240/media-3320818.pdf
It seems IXTH6N50D2 and 6N50 are not at all the same device, despite part of their designation being the same.
1 Like
Many, many thanks for your patience JMK!
1 Like
Hi
This is some sort of audio device I believe and could you tell me what its called and the principal of operation please, as far as I can see it seems crude. Please take no offence its just me and I don’t understand it ! at least I think I don’t hence a description would be nice 
for my own studies. I’m glad you have your heatsinking sorted 
It’s getting off topic now, but it is a class-A audio amplifier. The top mosfet is a constant current source, and the bottom mosfet has a potentiometer (P1) to set the output voltage (close to) 0V in rest. Then the audio input varies the conductance of the bottom fet, and the difference will go though the loudspeaker.
It’s crude, but it works. Reminds me of something similar with a few LM317 voltage regulators:
And it even has feedback.
1 Like
Thanks I will check that out
Great you have confirmed what I thought so thanks and yes it’s still a bit odd but I’m gonna look further I have an interest in Audio.
This topic was automatically closed 90 days after the last reply. New replies are no longer allowed.