Thanks for the inputs. I did not know that KP901 is not a JFET. Knowing that, the original schematic with a KP903 with a cascode would suffice at 60V.
I ordered some of KP901 and KP902 to measure and evaluate.
The original schematic has a current source in series with the 2SJ20. The resistor is just to simplify.
KP902 appears to work to 50V Vds.
I ordered some of KP901 and KP902 to measure and evaluate.
The original schematic has a current source in series with the 2SJ20. The resistor is just to simplify.
KP902 appears to work to 50V Vds.
Pa sez that a current source doesn't really count as an active stage, so it would still be a two-transistor circuit. 🙂
You may also want to take a look at Vfet 2SK98/2SJ38 GB and e-pray item Transistor silicon 2P926B (KP926B) USSR Lot of 1 pcs.
Hello woofertester. The schematic in your post above suggested that "IF" KP901 was instead a cascoded and tweaked J112, you have therein a built-in H2 generator; because Vgs=0 like taught by Mr. Pass.
Best
Anton
hmmmmmmm.... I will want to see Vds-Id curves for Vgs <<-1v It looks SIT-ish to me down there.
KP903 curves
Interesting family of curves for the KP903. From top to bottom, Vgs = +1, 0, -1, -2, -3.
This device is not happy at Vgs = +1V. Running the Vgs - Id curve reveals that the device saturates at Vgs = +0.8v. This device will require some degeneration to place it in its linear range. It looks pretty happy at Id = 300mA.
Interesting family of curves for the KP903. From top to bottom, Vgs = +1, 0, -1, -2, -3.
This device is not happy at Vgs = +1V. Running the Vgs - Id curve reveals that the device saturates at Vgs = +0.8v. This device will require some degeneration to place it in its linear range. It looks pretty happy at Id = 300mA.
Attachments
Thank you for the suggestion. I will give that a try. There is a box of Edcor transformers in my stash. I just watched your BAF 2013 video. Interesting that the devices do not need to be isolated from a common heatsink for lashing this up.
The table consists mainly normally off SIT's called BSIT's near bjt behaviour. There are real ones like audio КП801 and switch mode К(2)П802 and К(2)П926. There might be some exotic staff like 2П985-X. As far as I know most of them if not all were designed by the very same guy at different fabs during country's self-destruction. Most SITs were from Novosibirsk Fab almost "@" logo, which used to be a vacuum tube plant.
Beware 926 or ОП-15 or 802 do have huge spread/variations in current and/or cut-off voltage so one need quite a few of them to get a match. Capacitances are quite big as well.
Cheers
I notice that the original schematic as drawn , will place +60V on the gate of the SIT .if the tube's heater is not pre-heated at the power on of the output stage B+ . May as well just use a mosfet follower output stage if using a triode front end
316a
316a
Some tubes and some tube sockets have arrived. ZM's recommendation of 6DJ8 is attached. Ignore the Axis labels. The curves are plate voltage, plate current, grid voltage, etc. Transconductance is delta I plate / delta V grid.
The curves span from Vg = 0 to Vg = -2.0 in equal steps.
For 60V, biasing at 10mA looks good. Transconductance at 60V at 10mA bias is a shade under 11 mA / volt.
Paralleling both sections would give 20mA bias and 22 mA / V transconductance.
The curves span from Vg = 0 to Vg = -2.0 in equal steps.
For 60V, biasing at 10mA looks good. Transconductance at 60V at 10mA bias is a shade under 11 mA / volt.
Paralleling both sections would give 20mA bias and 22 mA / V transconductance.
Attachments
