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PING: Phil Hobbs, JFET Noise

Started by Jim Thompson August 9, 2016
On 10/08/2016 08:25, Phil Hobbs wrote:
> On 08/09/2016 02:50 PM, Phil Hobbs wrote: >> On 08/09/2016 01:26 PM, Jim Thompson wrote: >>> Phil, What makes a JFET less noisy than a enhancement mode CMOS >>> device? >>> >>> Would a depletion mode CMOS device be quieter? >>> >>> ...Jim Thompson >>> >> >> I don't know in any great detail. The physics of the carriers in the >> channel will be vaguely similar except that there's no chemical >> potential to drive the formation of a depletion region there is with a >> JFET or BJT. I suspect that there are a lot more traps and surface >> states when you have all those layers that the E field has to go >> through, compared with a nice buried epitaxial junction. >> >> That's backed up by the horrible 1/f noise of MOSFETs, but of course >> "traps and surface states" is the solid state guy's version of "market >> sentiment and program trading" on the Friday stock market report. ;) > > It would be sort of interesting to look at the noise behaviour of > lateral MOSFETs with their back gates pinned out separately. I bet the > 1/f noise would be a lot less if you ran the back gate at the edge of > forward bias. That would force all the channel conduction to happen > well away from the Si-SiO2 interface. > > You can't get those parts any more, of course.
Joerg recently pointed out a device that is still available (SST211).
On 08/09/2016 11:10 PM, Chris Jones wrote:
> On 10/08/2016 08:25, Phil Hobbs wrote: >> On 08/09/2016 02:50 PM, Phil Hobbs wrote: >>> On 08/09/2016 01:26 PM, Jim Thompson wrote: >>>> Phil, What makes a JFET less noisy than a enhancement mode CMOS >>>> device? >>>> >>>> Would a depletion mode CMOS device be quieter? >>>> >>>> ...Jim Thompson >>>> >>> >>> I don't know in any great detail. The physics of the carriers in the >>> channel will be vaguely similar except that there's no chemical >>> potential to drive the formation of a depletion region there is with a >>> JFET or BJT. I suspect that there are a lot more traps and surface >>> states when you have all those layers that the E field has to go >>> through, compared with a nice buried epitaxial junction. >>> >>> That's backed up by the horrible 1/f noise of MOSFETs, but of course >>> "traps and surface states" is the solid state guy's version of "market >>> sentiment and program trading" on the Friday stock market report. ;) >> >> It would be sort of interesting to look at the noise behaviour of >> lateral MOSFETs with their back gates pinned out separately. I bet the >> 1/f noise would be a lot less if you ran the back gate at the edge of >> forward bias. That would force all the channel conduction to happen >> well away from the Si-SiO2 interface. >> >> You can't get those parts any more, of course. > > Joerg recently pointed out a device that is still available (SST211). > >
Interesting, thanks. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net