I have a number of JFETs (J11[1-3]) and I want to match them. So I was measuring Idss (=Id with Vds=12V, Vgs=0) without any other components (setting Vds with bench supply, reading Id with bench DMM, Vds=12V because that is what I was planning to use them with). Naturally the component temperature increases when voltage is applied and Id decreases, as the speed of change slows down, around a range it stabilizes (I was using this value for matching). The issue is particularly for high Idss components (J111 is ~80mA) the temperature is very high (>100C), I actually thought it is going to break (and maybe it will if I let it like that). This made me question at what condition exactly I should measure Idss. Is there a standard procedure for this ? Which Vds should I use ? Does the (possibly different) temperature of the components have no effect ?