I recapped an old Dell power supply, as it has some useful voltages (-12, +12, +5, +3.3) and was more than enough powerful (160W) for most of the projects I do. Added a small load to the +5 rail and the voltages stabilised, that’s the light bulb.. spent a bit of time and built up matching circuit on Veroboard.


Initial testing was good, so tidied things up a little.


Set about measuring transistors to see the Vbe of each. Matching at 72F to within 2mV.


Did 100 of them, they are surprisingly close (all within about 5mV) so I have more matched and/or similar pairs than I thought! That’s good, means all the transistors installed can be identical.

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