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Replacement For Toshiba 2SK170/2SJ74
Replacement For Toshiba 2SK170/2SJ74
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Old 12th June 2019, 12:14 AM   #371
radule is offline radule  Serbia
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Quote:
Originally Posted by scott wurcer View Post
That's a relatively poor measure of Vp because the FET is in the subthreshold region. It is better to measure Vgs at two currents one above subthreshold like 200uA and one below Idss and use the FET equations given for Id vs Vgs. Two measurements two equations and solve for Vp and Idss.
Hi Scott,

I was puzzled with Vp of few samples of j74bl which I have.

They track prety well at working currents but Vp at 0.1uA is about 100mV different.

sample1: Idss-6.73mA, Vp @ 0.1uA -510mV, gm@5.5mA -34.31mS
sample2: Idss-6.76mA, Vp @ 0.1uA -618mV, gm@5.5mA -34.93mS

Is it about what you talked?
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Old 12th June 2019, 12:50 AM   #372
scott wurcer is offline scott wurcer  United States
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Quote:
Originally Posted by radule View Post
Hi Scott,

I was puzzled with Vp of few samples of j74bl which I have.

They track prety well at working currents but Vp at 0.1uA is about 100mV different.

sample1: Idss-6.73mA, Vp @ 0.1uA -510mV, gm@5.5mA -34.31mS
sample2: Idss-6.76mA, Vp @ 0.1uA -618mV, gm@5.5mA -34.93mS

Is it about what you talked?
In general yes, the deviation from square law behavior starts well before 0.1uA in my plots (which I lost in a drive crash).
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Old 17th June 2019, 10:45 PM   #373
DualTriode is offline DualTriode  United States
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Default Sziklai JFET pairs

Hello All,

Now that it is becoming more difficult to find complimentary pairs of P and N JFETS how will it work out making complimentary pairs of Sziklai JFET pairs.


For example a P channel version of a 2N5460+2N5457 and a complimentary N channel version of a 2N5457 + 2N5460.


Seems that very close Sziklai JFET pair matching of Idss and Gm could result in very low distortion.

Thanks DT

I have a ziplock baggie full of each of the 2 types of JFETís
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Old 18th June 2019, 09:02 PM   #374
franzm is offline franzm
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Hybrid pairs. Sometimes called Super G.
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Old 19th June 2019, 06:51 PM   #375
DualTriode is offline DualTriode  United States
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Hello,

The Hybrid pairs look cool too.

What my consideration is pairs made up of 1 N channel JFET and 1 P channel JFET.

This may be old news.

I have seen MOSFET compound pairs used in output stages but not JFET compound pairs used for low level amplification as a substitute for K170ís and J74ís. Should be able to get very close Idss and gm matching

Thanks DT

Finally have the Keysight SMU hardware speaking with the Keysight software. Should be able to trace some curves of such JFET pairs.
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Old 11th July 2019, 08:06 AM   #376
flancfuster is offline flancfuster  Europe
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For people looking for matched pairs or octet genuine Toshiba FETs, I recommend user NicMac from this forum. Thanks Nicolai.
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Old 11th July 2019, 11:45 AM   #377
kuly is offline kuly  Russian Federation
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2sk170------ smd 2sk209 (sot23)
2sj74-------smd,,????? (sot 23)

What SMD can I apply? J74. similar analog
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Old 11th July 2019, 12:16 PM   #378
Kovax is offline Kovax  Croatia
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If u looking for low noise then SST74, if not looking for low noise then MMBFJ270 or MMBFJ177
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Old 11th July 2019, 12:21 PM   #379
kuly is offline kuly  Russian Federation
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Thanks, I will try
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