On Sat, 8 Apr 2017 16:30:38 -0400, you wrote: >David wrote: > >> I mentioned this in connection with some manufacturers using gold >> doping in transistors which would not normally be expected to have >> gold doping. So you end up with a bunch of lessor named 2N3904s which >> meet the 2N3904 specifications but are useless if you were looking for >> low leakage diodes. > >I believe all 2N3904s and 2N3906s are gold doped. National's certainly >were (Processes 23 and 66), and TI's and Fairchild's are. Not heavily >doped, like 2N2369s (with storage times of ~20nS), but just enough to >bring the storage time down to ~100nS. 2N2219s, 2N2222s, and 2N4401s >are also lightly gold doped.
I ended up qualifying 2N3904s based on manufacturer and lot and I think we ended up using ones from Motorola. I wish detailed process information like National had was available from every manufacturer. What was funny was when we did this, the lower frequency transistors that I tested like the 2N5088/9 were much worse. >> If [4117 leakage is] 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. >> * * * >> 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 > >Same as any "guaranteed by design" spec -- by the device design. The >4117 series is unlike any other JFET -- the geometry is TINY, and the >4117 Idss is only 30-90uA (hundreds of times lower than other low-Idss >JFETs). [BTW, lowest Idss is why I recommend the 4117 over the 4118 and >4119 for use as a low-leakage diode. The 4118 and 4119 have higher Idss >-- up to 240uA for the 4118 and 600uA for the 4119 -- and tend to have >higher gate leakage, as well.] > >Best regards, > >Charles If the 10pA specification is guaranteed by design, then wouldn't they have to be testing the 1pA "A" parts? _______________________________________________ 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.
