Am 08.04.2017 um 17:52 schrieb David:
If they are not being tested, then where is the maximum specified leakage number coming from? For a small signal bipolar transistor it will typically be 25nA, 50nA, or 100nA, but the InterFET datasheet (1) shows 10pA maximum and 1pA maximum for the A versions.
The large print giveth and the small print taketh away. Usually there are footnotes and weasel words like "sample tested", "by characterisation" or "not production tested". The time such a small device sits on the wafer tester costs much more than the silicon. For 100 msec. At 1 pA it takes an eternity until the capacitances in the setup are charged. Just the waiting time makes such a diode or FET a premium part.
When this discussion of low leakage input protection started, I did a quick search for inexpensive alternatives to the 4117/4118/4119 JFETs and came up with nothing; all of the inexpensive JFETs are much worse until you get to premium devices. (1) I only picked the InterFET datasheet because it was the most readily available of the ones you mentioned. The current Fairchild and Linear Systems datasheets show the same thing.
Ouch, Interfet and data sheet in one sentence! But then they could condense it further and just give the abs.max. ratings. I have checked out my first 7 pairs of IF3602. Some have > 100 mA at Vgs=-0.5V, others don't have any drain current at all. I wanted to parallel 4 pairs for noise reasons, found just 2 pairs that are reasonably similar. At €50 a pop finding another matching 2 will cost a pretty penny probably. The noise spec also seems "optimistic" and there was troubling gate current with the 2 pairs, even at Vdd=2V. The 1/f corner seems to be OK at 30 Hz. Back to input protection: Someone in the sci.electronics.design group mentioned these < https://www.digikey.de/products/de?keywords=cmpd6001s > but, as usual, typical values, and watch the plot with the temperature as parameter. At least they are cheap. Also interesting, while not exactly low leakage diodes, are these USB3 lightning arrestors: < https://www.digikey.de/products/de?keywords=296-25509-1-nd > Looks like they don't spoil the timing. regards, Gerhard _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
