Most seem to specify 1uA, even at 25C. Can anyone point me to one that's affordable and more like 10nA? Most selection guides seem to miss out this feature! Greatly appreciate any feedback. -- Mike Perkins Video Solutions Ltd www.videosolutions.ltd.uk
Low MOSFET IDSS current
Started by ●December 9, 2017
Reply by ●December 9, 20172017-12-09
On 09/12/2017 23:07, Mike Perkins wrote:> Most seem to specify 1uA, even at 25C. Can anyone point me to one that's > affordable and more like 10nA? > > Most selection guides seem to miss out this feature! > > Greatly appreciate any feedback.Sorry, forgot to say, this has to be a P-channel -- Mike Perkins Video Solutions Ltd www.videosolutions.ltd.uk
Reply by ●December 9, 20172017-12-09
On Sat, 9 Dec 2017 23:09:07 +0000, Mike Perkins <spam@spam.com> wrote:>On 09/12/2017 23:07, Mike Perkins wrote: >> Most seem to specify 1uA, even at 25C. Can anyone point me to one that's >> affordable and more like 10nA? >> >> Most selection guides seem to miss out this feature! >> >> Greatly appreciate any feedback. > >Sorry, forgot to say, this has to be a P-channelOh. This is for a 2N7000/7002, n-channel: https://www.dropbox.com/s/zgj6xiv2s2pcyim/2n7000_off_leakage.pdf?raw=1 I think that's Win's data. A few pA. I'd guess that a small high-threshold p-channel would be similar. BSS84? They're just not production tested down there. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●December 9, 20172017-12-09
On 10/12/2017 01:16, John Larkin wrote:> On Sat, 9 Dec 2017 23:09:07 +0000, Mike Perkins <spam@spam.com> wrote: > >> On 09/12/2017 23:07, Mike Perkins wrote: >>> Most seem to specify 1uA, even at 25C. Can anyone point me to one that's >>> affordable and more like 10nA? >>> >>> Most selection guides seem to miss out this feature! >>> >>> Greatly appreciate any feedback. >> >> Sorry, forgot to say, this has to be a P-channel > > Oh. This is for a 2N7000/7002, n-channel: > > https://www.dropbox.com/s/zgj6xiv2s2pcyim/2n7000_off_leakage.pdf?raw=1 > > I think that's Win's data. A few pA. > > I'd guess that a small high-threshold p-channel would be similar. > BSS84? They're just not production tested down there.Many thanks. I have been looking at a number of datasheets and I discarded the BSS84 as I'd found a datasheet that gave an IDSS of 15uA and 60uA at two different temperatures. On closer inspection I see that this was at VDS of 50V. Another datasheet, this time for a BSS84L gives an IDSS max of 100nA, but at VDS of just 25V. So it looks as if I need to be more specific about the manufacturer and the specific part rather than assuming all those with the same generic number were the same! -- Mike Perkins Video Solutions Ltd www.videosolutions.ltd.uk
Reply by ●December 9, 20172017-12-09
John Larkin wrote...> > Mike Perkins wrote: >> Mike Perkins wrote: >>> Most seem to specify 1uA, even at 25C. Can anyone point >>> me to one that's affordable and more like 10nA? >> >> Sorry, forgot to say, this has to be a P-channel > > Oh. This is for a 2N7000/7002, n-channel: > >https://www.dropbox.com/s/zgj6xiv2s2pcyim/2n7000_off_leakage.pdf?raw=1 > > I think that's Win's data. A few pA. > > I'd guess that a small high-threshold p-channel would be > similar. BSS84? They're just not production tested down there.Most mosfets have remarkably-low leakage currents at room temperature. But it's expensive to test at low currents, and there's little demand for very low-current specs, so the datasheets list a much higher value, they're willing to test and stand behind. Mike, I recommend you purchase parts and vet them yourself for the application. Perform an incoming test, we call it. Here's a cute simple thing you can do with a power MOSFET. Connect it with a series resistor to brightly drive an LED. Next use a pot and test lead to apply a voltage to the gate that runs the LED at a partial brightness. Remove the lead so the gate is sitting disconnected, but holding the voltage you applied. Observe the LED remain at its set brightness, so the gate is remaining at that voltage, perhaps for hours, stored on the gate capacitance. Leakage I = C dV/dt. -- Thanks, - Win
Reply by ●December 10, 20172017-12-10
On 10/12/2017 02:46, Winfield Hill wrote:> John Larkin wrote... >> >> Mike Perkins wrote: >>> Mike Perkins wrote: >>>> Most seem to specify 1uA, even at 25C. Can anyone point >>>> me to one that's affordable and more like 10nA? >>> >>> Sorry, forgot to say, this has to be a P-channel >> >> Oh. This is for a 2N7000/7002, n-channel: >> >> https://www.dropbox.com/s/zgj6xiv2s2pcyim/2n7000_off_leakage.pdf?raw=1 >> >> I think that's Win's data. A few pA. >> >> I'd guess that a small high-threshold p-channel would be >> similar. BSS84? They're just not production tested down there. > > Most mosfets have remarkably-low leakage currents at room > temperature. But it's expensive to test at low currents, > and there's little demand for very low-current specs, so > the datasheets list a much higher value, they're willing > to test and stand behind. Mike, I recommend you purchase > parts and vet them yourself for the application. Perform > an incoming test, we call it. > > Here's a cute simple thing you can do with a power MOSFET. > Connect it with a series resistor to brightly drive an LED. > Next use a pot and test lead to apply a voltage to the gate > that runs the LED at a partial brightness. Remove the lead > so the gate is sitting disconnected, but holding the voltage > you applied. Observe the LED remain at its set brightness, > so the gate is remaining at that voltage, perhaps for hours, > stored on the gate capacitance. Leakage I = C dV/dt.Many thanks. Given Johns links to actual IDS currents, I was coming to the conclusion this might be down to the cost of testing. I'm aware that testing in a generic fixture down to sub uA is not a run of the mill expectation. I'm not in a position to test every component that could run into 1,000 or more, although batch testing might be a compromise. The BSS84L is about 5-10x the cost of similarly sized FETs, but hey! -- Mike Perkins Video Solutions Ltd www.videosolutions.ltd.uk
Reply by ●December 10, 20172017-12-10
On 9 Dec 2017 18:46:25 -0800, Winfield Hill <hill@rowland.harvard.edu> wrote:>John Larkin wrote... >> >> Mike Perkins wrote: >>> Mike Perkins wrote: >>>> Most seem to specify 1uA, even at 25C. Can anyone point >>>> me to one that's affordable and more like 10nA? >>> >>> Sorry, forgot to say, this has to be a P-channel >> >> Oh. This is for a 2N7000/7002, n-channel: >> >>https://www.dropbox.com/s/zgj6xiv2s2pcyim/2n7000_off_leakage.pdf?raw=1 >> >> I think that's Win's data. A few pA. >> >> I'd guess that a small high-threshold p-channel would be >> similar. BSS84? They're just not production tested down there. > > Most mosfets have remarkably-low leakage currents at room > temperature. But it's expensive to test at low currents, > and there's little demand for very low-current specs, so > the datasheets list a much higher value, they're willing > to test and stand behind. Mike, I recommend you purchase > parts and vet them yourself for the application. Perform > an incoming test, we call it. > > Here's a cute simple thing you can do with a power MOSFET. > Connect it with a series resistor to brightly drive an LED. > Next use a pot and test lead to apply a voltage to the gate > that runs the LED at a partial brightness. Remove the lead > so the gate is sitting disconnected, but holding the voltage > you applied. Observe the LED remain at its set brightness, > so the gate is remaining at that voltage, perhaps for hours, > stored on the gate capacitance. Leakage I = C dV/dt.You can do interesting things with a 2N7000: https://www.dropbox.com/s/i1sw7shpex29wf1/2N7000.jpg?raw=1 Briefly touch the gate to B+, ground, or the fet drain to get three brightness levels. The gate leakage can't be mant electrons per second. There is a simple push-push on/off switch effect. It might be possible to demonstrate electron quantization somehow. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●December 10, 20172017-12-10
On Sun, 10 Dec 2017 14:37:30 +0000, Mike Perkins <spam@spam.com> wrote:>On 10/12/2017 02:46, Winfield Hill wrote: >> John Larkin wrote... >>> >>> Mike Perkins wrote: >>>> Mike Perkins wrote: >>>>> Most seem to specify 1uA, even at 25C. Can anyone point >>>>> me to one that's affordable and more like 10nA? >>>> >>>> Sorry, forgot to say, this has to be a P-channel >>> >>> Oh. This is for a 2N7000/7002, n-channel: >>> >>> https://www.dropbox.com/s/zgj6xiv2s2pcyim/2n7000_off_leakage.pdf?raw=1 >>> >>> I think that's Win's data. A few pA. >>> >>> I'd guess that a small high-threshold p-channel would be >>> similar. BSS84? They're just not production tested down there. >> >> Most mosfets have remarkably-low leakage currents at room >> temperature. But it's expensive to test at low currents, >> and there's little demand for very low-current specs, so >> the datasheets list a much higher value, they're willing >> to test and stand behind. Mike, I recommend you purchase >> parts and vet them yourself for the application. Perform >> an incoming test, we call it. >> >> Here's a cute simple thing you can do with a power MOSFET. >> Connect it with a series resistor to brightly drive an LED. >> Next use a pot and test lead to apply a voltage to the gate >> that runs the LED at a partial brightness. Remove the lead >> so the gate is sitting disconnected, but holding the voltage >> you applied. Observe the LED remain at its set brightness, >> so the gate is remaining at that voltage, perhaps for hours, >> stored on the gate capacitance. Leakage I = C dV/dt. > >Many thanks. > >Given Johns links to actual IDS currents, I was coming to the conclusion >this might be down to the cost of testing. I'm aware that testing in a >generic fixture down to sub uA is not a run of the mill expectation. > >I'm not in a position to test every component that could run into 1,000 >or more, although batch testing might be a compromise. > >The BSS84L is about 5-10x the cost of similarly sized FETs, but hey!I test a few parts and assume that future purchases will be similar, at leat within a factor of 10 or so. Semiconductors tend to be very consistent. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●December 11, 20172017-12-11
Mike Perkins wrote...> > I'm not in a position to test every component that could > run into 1,000 or more, although batch testing might be > a compromise.Batch testing should be fine. -- Thanks, - Win
Reply by ●December 11, 20172017-12-11
Winfield Hill <hill@rowland.harvard.edu> wrote:> Mike Perkins wrote...>> I'm not in a position to test every component that could >> run into 1,000 or more, although batch testing might be a compromise.> Batch testing should be fine.Nobody does AQL any more? https://en.wikipedia.org/wiki/Acceptable_quality_limit
