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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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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 online now 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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