I got a set of pcb's from Tea-Bag GB, they are really nice, thanks! I have two questions so far:
1) why do you need to parallel FE jfets Q3A,B and Q4A,B?
2) why two LEDs and which to buy -- blue, but there are many blue LEDs, does it matter?
1) why do you need to parallel FE jfets Q3A,B and Q4A,B?
2) why two LEDs and which to buy -- blue, but there are many blue LEDs, does it matter?
1) if you have GR instead of BL you can parallel them to the wanted Idss
2) for SS only one blue on one side, or two red on one side
for IRF you may need two blue for one side, higher Vgs...!
2) for SS only one blue on one side, or two red on one side
for IRF you may need two blue for one side, higher Vgs...!
I haven't seen one, but I can deliver the executive summary:
Looks a lot like the SJEP R100, but with obvious difference in Vgs offset.
Has a larger Vds range in which it operates in the "linear" or "ohmic" region,
and you can see that from the characteristic curves vs the R100.
So for a little more complicated (maybe) bias arrangement, you can get a
little less intrinsic distortion and lower Drain resistance.
(two ways of describing the same thing) Cascode it imaginatively and you
can amplify the effect.
😎
Looks a lot like the SJEP R100, but with obvious difference in Vgs offset.
Has a larger Vds range in which it operates in the "linear" or "ohmic" region,
and you can see that from the characteristic curves vs the R100.
So for a little more complicated (maybe) bias arrangement, you can get a
little less intrinsic distortion and lower Drain resistance.
(two ways of describing the same thing) Cascode it imaginatively and you
can amplify the effect.
😎
I wrote you why I need it - to save me some time on the bench , while preparing to make a pair of ultimate Papa's Koan amps
I finally have worthy solution ........ and it seems I like fiddlin' with sims , after all these years without using them proggies
whatever ...... whenever you need a fish , just whistle 😉
I finally have worthy solution ........ and it seems I like fiddlin' with sims , after all these years without using them proggies
whatever ...... whenever you need a fish , just whistle 😉
Blasphemy be damned! Sims are a way to build circuits with unobtainium parts. Even parts that have never existed. 😀
Just my excuse to remain in ignorance. Feel like siming the bridged version with bottom feedback resistors tied together? I'll build it, but it takes longer.
Yo Pa - I needed prediction for few values for servo circ and level shifter .......
I solved my dilemmas in simple way - - looking at Pass SIT-1 U/I graph , finding Ugs voltage for 22V/2A35 (ring a bell ?) , then finding by LTSpice shown Ugs voltage of SJEP'100 at 2A35 ;
so - for static biasing sim in LTSpice , PapaSit is SJEP'100 + DC Vgen of 5.7294V tied to gate ; 'course plus of it connected to gate , minus to other end , which will drive precious unobtanium
ya nutz ? wrapped my head around xformers ages ago , but no Bubba - you'll not force me to put them in sim
find me a working model , I'll sim it ; no other way
The following LTSpice model is courtesy of my graduate student who used it to sim power switching for his dissertation. One warning, no one I know has got the characteristic soft transition into saturation of a SemiSouth JFET modeled well in spice, despite some tries. He even worked at it for awhile until I stopped him because us power switching guys don't worry about precise modeling of the transition to saturation. We're trying to get out of it as quick as possible! So, no guarantee that this will predict subtle distortion properties convincingly.
.subckt SJDP120R085 D G S\n.param R=530m ; R_gate\nBg G Gi I=-UpLim(47m*\n+ uRamp(V(D,Di))**3.5,10,1)/R\nRg G Gi {R} tc=-3m\nRd D Di 70m tc=4m 40u\nCsd S Di 3p\nCgd G Di 13p\nJi Di Gi S SJDP120R085\n.model SJDP120R085 njf\n+ Vto=-4 Beta=45 B=30m\n+ Lambda=500u Vk=2k5 Alpha=20u\n+ Is=1f N=3.4\n+ Isr=1n Nr=6.8\n+ Cgd=1n Cgs=610p Pb=2.6 M=0.92\n+ Kf=100f Af=1\n+ VtoTC=-2m4 BetaTCe=-0.65 Xti=86\n.ends SJDP120R085
Your welcome! You may notice that the model includes temperature variations. The value of that won't be lost on a Class A crowd like you all! 😀
BTW, the credit for this model belongs to Dave Sheridan, SemiSouth's long time VP for Engineering. My student "borrowed" it for his work.
