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Greatly Improved JFET MatcherVerified
Based on the Greatly Improved JFET Matcher
From the post
So moving on from RG's JFET matcher which measures VGS (or more precisely, the voltage at which RDS is 10K) , this is another version by Sebastian from runoffgroove which allows you to measure VP and IDSS depending on the position of the switch.
The centre off position should be used to insert and remove the JFETs, and as long as you keep the orientation of the switch the same as shown in the layout, up measures IDSS and down measures VP.
A combination of these two layouts will allow you to match JFETs in a number of different ways, so use the appropriate one depending on what characteristic you are required to match, but if in doubt which to use, having VP and IDSS close means the JFETs are more effectively matched and so this method is probably preferable.
And an updated version which is even more simple and will allegedly give more accurate matches:
Schematic
This is a board layout, a drawing of where each part goes, and the post may link the schematic it was drawn from. Open the layout at Tagboard Effects. No KiCad fragment has been drawn for this circuit yet.
Parts list 5 rows
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| Ref | Value | Normalized | Type | Notes |
|---|---|---|---|---|
| Resistors 2 | ||||
| ×1 | 10R | 10 | read from the layout by eye | |
| ×1 | 10M | 10M | read from the layout by eye | |
| Capacitors 1 | ||||
| ×1 | 47u | 47u | electrolytic, drawn axial; read from the layout by eye | |
| ICs 1 | ||||
| ×1 | TLC2262 | TLC2262 | legend: IC is TLC2262 or similar; read from the layout by eye | |
| Switches 1 | ||||
| Switch | DPDT on/off/on | DPDT ON/OFF/ON | toggle; up Idss, centre off, down Vp; read from the layout by eye | |