They were Fairchild Stealth diodes, 200v 6a I believe. I found them on closeout, so bought a lot of 400 or so.
Don't have any left, have been replaced in my stockpile by standard MSRF860G, partly on Salas recommendation.
To measure Vf for triplets and quartets, what resistor value should I use for tests if I go to measure all LEDs together connected respectively as 3 and 4 devices with 9V?
My concern is coming up from an empirical test when I measure single LED, then I sum all my measured LED and then I calculating the result. However, I have other result when I measure 3 and 4 LED connected together with the same 1.5K resistor. I assume that LED has own resistance added and this is what differentiate test results.
My concern is coming up from an empirical test when I measure single LED, then I sum all my measured LED and then I calculating the result. However, I have other result when I measure 3 and 4 LED connected together with the same 1.5K resistor. I assume that LED has own resistance added and this is what differentiate test results.
Thank you Salas.
Finally got myself together and did some calc
Using "Id (ccs) = Idss (1 - (Vgs / Vp))2"
and "Vgs = Id x Rs"
For a K369 idss = 10.3mA and Rs = 3.9ohm I estimate Id = 8.9mA
For both Q1 + Q2 we have a total of 17.8mA Idling
I want 4volts on top of folded collector R4 (2200), so current on R4 is 1.818mA
Total current on R13 (1200) is then 19.62mA
Vdrop on R13 is 23.54V
Having 8V on the folded base we have 8,6V on the emitter of Q3 so we already have a Vdrop of 23.54 + 8.6 = 32.14V
If I set Vp = 35V than I need to drop 35-32.14 = 2.86V on R12//Vr1 for a current of 19.62mA and that gives me 146ohms.
So it seemed I needed to increase R13 or R12/vr1..... but then I remembered you suggested to use alternative Vp.... if I lower Vp to 34v, everything is in place naturally.
Now I only need to drop 1.86V on R12//Vr1 and the resulting resistance is 95ohm.
Quite flexible and brilliant engineering.
Well, I take this long silence like with caution.
Please take in consideration this simulation uses less than perfect fet models so it can only be used to evaluate DC conditions as well as dissipation values in the amp.
It serves no other purpose and I strongly suggest anyone who has any doubts about the circuit should post it here and wait for Salas information.
Please take in consideration this simulation uses less than perfect fet models so it can only be used to evaluate DC conditions as well as dissipation values in the amp.
It serves no other purpose and I strongly suggest anyone who has any doubts about the circuit should post it here and wait for Salas information.
The simulation has slightly different values....
There are only 8V on the emitter of Q3 so Vdrop is 23.54+8=31.54..... this leaves 3.46v to be droped over the resistor ... in this case it is not 146 but 176r (250 // 600).
The sim works ok but as you say the best way is to use a breadboard
There are only 8V on the emitter of Q3 so Vdrop is 23.54+8=31.54..... this leaves 3.46v to be droped over the resistor ... in this case it is not 146 but 176r (250 // 600).
The sim works ok but as you say the best way is to use a breadboard
What to say... Its a typical sim. The Jfet models give bit less gain than actual its a remark.