2N5458 jfet

[Tekko]

I fount two old gold leg 2N5458 jfets in a bag of parts and now i wonder if i could use them to anything.

[AndrewT]

first: download the datasheet and identify the leadouts.
second: assemble an Idss measuring jig. 9V battery, 1k0 1% resistor, set of 3 croc ended leads.
third: measure the Idss at your actual test voltage.

This confirms you have working jFETs, it also gives an idea of what type of circuit would suit them.

[Tekko]

First, already done, thats how i found out they were jfets.

Second, does 1k go betweek G and D or G and S ? i dont have any wires with croc clips in one end so i'll have to solder.

[AndrewT]

Idss is measured with Vgs=0.000mV
You ensure Vgs = 0 by shorting these two leads together. One croc clip shorts the two gate & source leads.
The resistor can be attached to the +ve battery terminal or the -ve battery terminal. Again a croc clip does this.
The third croc clip brings +ve to the drain lead of an Nch jFET. The G+S go to the -ve.

Measure Vdrop of the resistor and measure the Vds of the jFET. These should sum to the battery voltage.