Suitable jfet for an zero GNFB amp?

[roender]

Characteristics:

low noise
Yfs > 10mS
zero Ids (Vgs) drift with temperature at any current in the range of 2...8mA

There is such device?

 

[h_a]

2SK170/2SJ74
2SK369

However there's no data on temperature dependence of drain current in the datasheet.

Have fun, Hannes

EDIT: I just saw your RMI-amp uses the 2SK170; so what is your particular interest, the zero tempco for ID? I don't remember that spec in any jfet datasheet, but I only have the abbreviated pdfs.

 

[john curl]

I don't think this will have 0 tc Too much transconductance. You need about 0.7V bias voltage to get 0 tc, and a 170 will not get you there easily.

 

[roender]

I don't think this will have 0 tc Too much transconductance. You need about 0.7V bias voltage to get 0 tc, and a 170 will not get you there easily.

Zero Tc for k170 is at 13...14mA but at this current is has very high transconductance and it not sound good.

 

[bogdan_borko]

Characteristics:

low noise
Yfs > 10mS
zero Ids (Vgs) drift with temperature at any current in the range of 2...8mA

There is such device?

I don`t think you`ll easily find a jfet like that.
btw. I`m working on non-global-feedback amplifier and I`m using 2SK170BL/2SJ74BL in the input stage but with servo incuded.

 

[roender]

Linear Systems j308/j309/j310 maybe?

 

[homemodder]

Roender, you have mail, let me know if it works out.

 

[Lumba Ogir]

Roender,

zero Ids (Vgs) drift with temperature at any current in the range of 2...8mA There is such device?

There is not (on this planet).

 

[AndrewT]

Feucht wrote a paper on temp coef of Jfet.
I seem to recall he said the Vgs should be 800mV above Vpinchoff for closest to temp comp.
Then the CCS is set up to ensure it too has temp comp at the required current.

 

[roender]

I seem to recall he said the Vgs should be 800mV above Vpinchoff for closest to temp comp.

VGS = VP + 0.63V for zero TC
http://www.tkhifi.com/div/Erno_Borbely_fet_articel_1.pdf

 

[jacco vermeulen]

Example , not exactly low noise but it has a nice zero TC curve.

 

[roender]

Example , not exactly low noise but it has a nice zero TC curve.

Wow, 2n5564 price tag 56GBP at Farnell UK
Thanks, but no thanks!

 

[jacco vermeulen]

WoW

 

[roender]

Thanks Jacco

2n5566 = 20mV delta Vgs
2n5565 = 10mV delta Vgs
2n5564 = 5mV delta Vgs

Zero TC at Id around 4mA
Yfs around 10mS aT Id=4mA


2n5564 seems to be a good candidate for my amplifier but is hard to find and very expensive

 

[homemodder]

You could also have a look at interfet, they have some good jfets. Replacements for japanese jfets, and theres also a p channel part. Full specs are not given beyond the obvious but they should be close to the japanese counterparts. IFN146 and 147 are very good. Heres a link maybe theres something you could use, www.interfet.com/pdf/j_equiv.pdf.

Jacco you seem to know where to obtain some difficult parts, have anywhere you know I could get hold of 2SC3067 in big quantaties, but in Europe, Im tired of ordering from east.