Don't know that circuit. Does the DN have a gate stopper resistor? Nice and close to the gate lead?
Yes the DN has a 330 ohm gate stopper resistor but I breadboaded it on a solderless board.
So I have 4 versions of CS:
1 two DN2540 cascode
2 one DN2540
3 one 2SK170
4 one 2sk170 inside a DN2540 cascode
the pure DN2540 versions 1 and 2 allow hum to pass through.
I'm using a cheap wall power transformer power supply.
So I have 4 versions of CS:
1 two DN2540 cascode
2 one DN2540
3 one 2SK170
4 one 2sk170 inside a DN2540 cascode
the pure DN2540 versions 1 and 2 allow hum to pass through.
I'm using a cheap wall power transformer power supply.
Depends on what you mean by 'better'. Rdyn is about 20-30% higher. Otherwise, it's a matter of availability. There were times when the IXYS part was unobtanium, but the DN2540 has always been scarce. I would use whichever was available; I don't think there will be any difference in normal (not approaching design limits) service.
Poinz
Poinz
Don't forget the 2SK170 come in three IDSS ranges (Vgs = 0V) :
2SK170GR : 2,6 to 6,5 ma
2SK170BL : 6 to 12 ma
2SK170V : 10 to 20 ma
The 2SK170 is very good as current source and source follower buffer but personally, I will never use them as commun source amplifier ...
Alain. 🙂
I'm just testing the 2SK170 because that was what Nelson Pass has in his JFET BOZ.
I plan on using the current source devices on a tube preamp next, modding the 12ax7a or 7247 in the EICO ST70.
The DN2540 has been used on cathode end of power tubes. What is a typical voltage to get good CMRR?
No problem using the DN2540 for 0.5mA to 2mA and a 2K resistor between the gate and the source is safe.
The DN2540 is very good for high voltage use in tubes circuits, VDS up to 400V but a minimum VDS over 10V is the best. A good alternative to replace the DC load resistor or choke in plate circuits to make some kind of SRPP circuit.
The 2SK170 is a low voltage device, a maximum VDS of 40V but you better use it in a range from 2 to 20V, then no good for plate circuit but OK for cathode circuit like in a "long tail pair" phase splitter.
You just have to take care not exceeding the maximun power dissipation, you may need a heatsink in many cases, sometime a very big one for the TO220 DN2540 version with a high current ...
For both 2SK170 or DN2540, you should use a multiturns trimpot to adjust the bias because there can be a big current difference between different specimens and datasheets curves, IDSS and Yfs (Forward transfer admittance). Also keep in mind JFET current drop with temperature raise ...
Alain. 🙂
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