OK this one is from 30-80 mA, so may be that 2 k trimmer could not reach enough Ugs to go down to 2 mA. Than add serial resistor to set Id=2 mA
Ideally would be LED current equal Sziklai current, that means both CCS BJTs same current, same Ube characteristic, electricaly plus thermally (coupled together) makes CCS very stable. 😎
P.S. BF246A Uds should be around 10 V for good regulation and AC suppression, if Rgs drops too much to get 2 mA, than lower 12 k to 10 k or less just to maintain Uds=10 Vmin 🙂
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Jack of all trades, master ... joke 😀
Yes I see you're very capable and most handy, congratulations
Hi Gerhard
Three amp stages only (input, output, CCS) in TSSA but all black of small signal transistors on your PCBs. 6800 uF feedback elcos 😱
Niceeee 😎
Good progress Joachim.
When i am done the gerber files, the BOM and the Pick and place data.
The board is made with SMT for the frontend.
I can produce the board with all SMT on them, but with above files i will upload everyone else can also.
Regarding the mosfet drivers. Is there an reliable source for 2SK216 and 2SJ79?? Or should wi install IRF instead???
When i am done the gerber files, the BOM and the Pick and place data.
The board is made with SMT for the frontend.
I can produce the board with all SMT on them, but with above files i will upload everyone else can also.
Regarding the mosfet drivers. Is there an reliable source for 2SK216 and 2SJ79?? Or should wi install IRF instead???
Hi Sonnya
SMT parts are perfect choice here, since there are a lot small signal BJTs connected between themselves only. Try to make as compact PCB as possible.
There are few suppliers that can provide 2SJ79/2SK216. These are lateral mosfets (transconductance falls with higher temperature) so no problem with thermal runaway, also have integrated gate protection zeners - perfect drivers. Try to find these not IRFs. 😉
I cannot wait to see your PCB
SMT parts are perfect choice here, since there are a lot small signal BJTs connected between themselves only. Try to make as compact PCB as possible.
There are few suppliers that can provide 2SJ79/2SK216. These are lateral mosfets (transconductance falls with higher temperature) so no problem with thermal runaway, also have integrated gate protection zeners - perfect drivers. Try to find these not IRFs. 😉
I cannot wait to see your PCB
I can get them still although i think Renaisas stopped production of this transistors. Exicon makes laterals but not TO220. One solution is to use big ones for the drivers too.
Sure, i use 2SJ77 and 2SK214. They can stand enough voltage. I really whould not like to go to hexfets. I think laterals sound better, especially when you go down the drain.
They are excellent constant current souces.
They are excellent constant current souces.
Second solution:
Raise frontend current 5x
Gateresistor reduced 5x
Maybe change the feedback network by reducing it 2x.
5mA in the front stage but still only 1mA in the input pair.
This Way the drive impedance for the mosfet is 5x lower. I Think this Will improve the thd performance simelar without the mosfet drivers.
Raise frontend current 5x
Gateresistor reduced 5x
Maybe change the feedback network by reducing it 2x.
5mA in the front stage but still only 1mA in the input pair.
This Way the drive impedance for the mosfet is 5x lower. I Think this Will improve the thd performance simelar without the mosfet drivers.
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Sure, that will work too. Nevertheless i build the version with driver first and then we can compare.