On Monday, September 11, 2023 at 5:33:14 AM UTC-7, John Larkin wrote:> On Mon, 11 Sep 2023 11:01:46 +0100, piglet <erichp...@hotmail.com> > wrote: > >On 11/09/2023 4:16 am, whit3rd wrote:> >> So, to expect this in future, should we assume the B-E breakdown creates light, and > >> the collector current is a photodiode detecting that light? That does explain the > >> effect, and predicts emitter current proportional to collector current. > > > >Yes, I think you meant collector current proportional to emitter > >current?> PV optocouplers are great for generating a quiet floating voltage, > but a transistor is cheaper.Cheaper, yes, but not durable (the base breakdown makes dirt move on the transistor surface, kills the base leakage). The passivation of a transistor assumes B-E voltages an order of magnitude lower than breakdown, and in the opposite direction. You'll hate the current transfer ratio of that 'PV optocoupler', but the light source has much better aging characteristics than the transistor does.
NPN in unusual quadrant
Started by ●September 5, 2023
Reply by ●September 12, 20232023-09-12
Reply by ●September 12, 20232023-09-12
On Mon, 11 Sep 2023 22:57:24 -0700 (PDT), whit3rd <whit3rd@gmail.com> wrote:>On Monday, September 11, 2023 at 5:33:14?AM UTC-7, John Larkin wrote: >> On Mon, 11 Sep 2023 11:01:46 +0100, piglet <erichp...@hotmail.com> >> wrote: >> >On 11/09/2023 4:16 am, whit3rd wrote: > >> >> So, to expect this in future, should we assume the B-E breakdown creates light, and >> >> the collector current is a photodiode detecting that light? That does explain the >> >> effect, and predicts emitter current proportional to collector current. >> > >> >Yes, I think you meant collector current proportional to emitter >> >current? > > >> PV optocouplers are great for generating a quiet floating voltage, >> but a transistor is cheaper. > >Cheaper, yes, but not durable (the base breakdown makes >dirt move on the transistor surface, kills the base leakage). The passivation of >a transistor assumes B-E voltages an order of magnitude lower than breakdown, >and in the opposite direction. > >You'll hate the current transfer ratio of that 'PV optocoupler', but the light source has much >better aging characteristics than the transistor does.A phototransistor doesn't damage itself. It biases its own b-e junction forward about 0.6 volts. The official PV couplers make, typically, 8 volts and 30 uA. They are just a string of photodiodes in series. They usually make more volts and uA than specified. Maybe that's to account for degrdation, but more likely it's because LEDs have kept getting better.
Reply by ●September 12, 20232023-09-12
On 11/09/2023 15:16, John Larkin wrote:> On Mon, 11 Sep 2023 08:50:54 -0400, Phil Hobbs > <pcdhSpamMeSenseless@electrooptical.net> wrote: > >> On 2023-09-11 08:32, John Larkin wrote: >>> On Mon, 11 Sep 2023 11:01:46 +0100, piglet <erichpwagner@hotmail.com> >>> wrote: >>> >>>> On 11/09/2023 4:16 am, whit3rd wrote: >>>>> On Sunday, September 10, 2023 at 12:55:12?PM UTC-7, John Smiht wrote: >>>>>> On Sunday, September 10, 2023 at 7:57:03?AM UTC-5, Piglet wrote: >>>>>>> On 06/09/2023 03:38, John Larkin wrote: >>>>>>>> On Wed, 6 Sep 2023 02:31:04 -0000 (UTC), Phil Hobbs >>>>>>>> <pcdhSpamM...@electrooptical.net> wrote: >>>>>>>> >>>>>>>>> John Larkin <jla...@highlandSNIPMEtechnology.com> wrote: >>>>> >>>>>>>>>>>> Now pull the base negative, through a current-limiting resistor. What >>>>>>>>>>>> happens? >>>>>>>>>>> >>>>>>>>>>> Nothing until you exceed the emitter base reverse breakdown (or >>>>>>>>>>> collector base breakdown) voltage, >>>>>>>>>> >>>>>>>>>> Not literally nothing, but not much interesting. It gets more >>>>>>>>>> interesting when the base zeners. >>>>>>>>>> >>>>>>>>>>> >>>>>>>>>>> Bitter-base is usually about 5V >>>>>>>>>>> >>>>>>>>>>> Behaves kind of like a zener diode and damages the transistor. >>>>> >>>>>>>>> Haven’t tried it, at least not on purpose, but I’d guess that when the >>>>>>>>> avalanche starts, most of the electrons will get sucked up by the >>>>>>>>> collector. >>>>>>>>> >>>>>>>>> Since it’s the electrons and not the holes that do the avalanching in >>>>>>>>> silicon, that might partially suppress the avalanche. If that were true, >>>>>>>>> putting a positive voltage on the collector would make the base voltage >>>>>>>>> slightly more negative. >>>>>>>>> >>>>>>>>> Cheers >>>>>>>>> >>>>>>>>> Phil Hobbs >>>>>>>> >>>>>>>> I'd expect that zenering fills the b-e junction with lots of carriers, >>>>>>>> and some find their way into the collector. I don't know how many. >>>>>>>> >>>>>>>> Probably a lot less than foward base current. >>>>>>>> >>>>>>>> I suppose I should try it. >>>>>>>> >>>>>>> Did you try it? I did today with a junk box NPN and results are kind of >>>>>>> as expected: >>>>>>> >>>>>>> <https://www.dropbox.com/scl/fi/rqr7n3uunosswqhx4e59h/NPNunusualQuadrant.pdf?rlkey=6kcqwz3soawgxws2ouhbdktq3&raw=1> >>>>> >>>>>> Very good, Piglet. That is very linear which I did not expect. Your data results in >>>>>> Ic(nA) = 9.2536Veb - 74.33 >>>>> >>>>> So, to expect this in future, should we assume the B-E breakdown creates light, and >>>>> the collector current is a photodiode detecting that light? That does explain the >>>>> effect, and predicts emitter current proportional to collector current. >>>> >>>> Yes, I think you meant collector current proportional to emitter >>>> current? We did discusss all this back in 2015 under the thread "a very >>>> silly circuit". About 25 years ago I think Stephen Woodward posted a >>>> design idea in ED magazine using the effect to create a tiny negative >>>> bias for opamp offset nulling in a positive rail only environment. >>>> >>>> piglet >>> >>> PV optocouplers are great for genereating a quiet floating voltage, >>> but a transistor is cheaper. >>> >>> I guess a regular, transistor type optocoupler, will generate a >>> floating voltage too. Something else to try. >>> >> >> It will, but you have to accept an efficiency on the order of CTR/beta, >> i.e. something below 0.1%. > > One could parallel the c-b and b-e junctions. Might help a little. > >> >> Cheers >> >> Phil Hobbs > > OK for some tiny bias thing, probably not for running motors. > > This would be another curiosity measurement. You never know if such a > thing might be useful some day. >Here are some measurements I just made: <https://www.dropbox.com/scl/fi/jp7r2vkrqo8npkf2kws0t/OptoCoupler_PV.pdf?rlkey=cg5o780xvyjdepe74k750799q&raw=1> Seems bulk of the goodness comes from the C-B junction and paralleling E+C makes hardly any difference. piglet
Reply by ●September 12, 20232023-09-12
On 11/09/2023 13:50, Phil Hobbs wrote:> On 2023-09-11 08:32, John Larkin wrote: >> On Mon, 11 Sep 2023 11:01:46 +0100, piglet <erichpwagner@hotmail.com> >> wrote: >> >>> On 11/09/2023 4:16 am, whit3rd wrote: >>>> On Sunday, September 10, 2023 at 12:55:12?PM UTC-7, John Smiht wrote: >>>>> On Sunday, September 10, 2023 at 7:57:03?AM UTC-5, Piglet wrote: >>>>>> On 06/09/2023 03:38, John Larkin wrote: >>>>>>> On Wed, 6 Sep 2023 02:31:04 -0000 (UTC), Phil Hobbs >>>>>>> <pcdhSpamM...@electrooptical.net> wrote: >>>>>>> >>>>>>>> John Larkin <jla...@highlandSNIPMEtechnology.com> wrote: >>>> >>>>>>>>>>> Now pull the base negative, through a current-limiting >>>>>>>>>>> resistor. What >>>>>>>>>>> happens? >>>>>>>>>> >>>>>>>>>> Nothing until you exceed the emitter base reverse breakdown (or >>>>>>>>>> collector base breakdown) voltage, >>>>>>>>> >>>>>>>>> Not literally nothing, but not much interesting. It gets more >>>>>>>>> interesting when the base zeners. >>>>>>>>> >>>>>>>>>> >>>>>>>>>> Bitter-base is usually about 5V >>>>>>>>>> >>>>>>>>>> Behaves kind of like a zener diode and damages the transistor. >>>> >>>>>>>> Haven’t tried it, at least not on purpose, but I’d guess that >>>>>>>> when the >>>>>>>> avalanche starts, most of the electrons will get sucked up by the >>>>>>>> collector. >>>>>>>> >>>>>>>> Since it’s the electrons and not the holes that do the >>>>>>>> avalanching in >>>>>>>> silicon, that might partially suppress the avalanche. If that >>>>>>>> were true, >>>>>>>> putting a positive voltage on the collector would make the base >>>>>>>> voltage >>>>>>>> slightly more negative. >>>>>>>> >>>>>>>> Cheers >>>>>>>> >>>>>>>> Phil Hobbs >>>>>>> >>>>>>> I'd expect that zenering fills the b-e junction with lots of >>>>>>> carriers, >>>>>>> and some find their way into the collector. I don't know how many. >>>>>>> >>>>>>> Probably a lot less than foward base current. >>>>>>> >>>>>>> I suppose I should try it. >>>>>>> >>>>>> Did you try it? I did today with a junk box NPN and results are >>>>>> kind of >>>>>> as expected: >>>>>> >>>>>> <https://www.dropbox.com/scl/fi/rqr7n3uunosswqhx4e59h/NPNunusualQuadrant.pdf?rlkey=6kcqwz3soawgxws2ouhbdktq3&raw=1> >>>> >>>>> Very good, Piglet. That is very linear which I did not expect. Your >>>>> data results in >>>>> Ic(nA) = 9.2536Veb - 74.33 >>>> >>>> So, to expect this in future, should we assume the B-E breakdown >>>> creates light, and >>>> the collector current is a photodiode detecting that light? That >>>> does explain the >>>> effect, and predicts emitter current proportional to collector current. >>> >>> Yes, I think you meant collector current proportional to emitter >>> current? We did discusss all this back in 2015 under the thread "a very >>> silly circuit". About 25 years ago I think Stephen Woodward posted a >>> design idea in ED magazine using the effect to create a tiny negative >>> bias for opamp offset nulling in a positive rail only environment. >>> >>> piglet >> >> PV optocouplers are great for genereating a quiet floating voltage, >> but a transistor is cheaper. >> >> I guess a regular, transistor type optocoupler, will generate a >> floating voltage too. Something else to try. >> > > It will, but you have to accept an efficiency on the order of CTR/beta, > i.e. something below 0.1%. > > Cheers > > Phil Hobbs >I made some tests and I think you are correct, lower beta gives higher output. <https://www.dropbox.com/scl/fi/jp7r2vkrqo8npkf2kws0t/OptoCoupler_PV.pdf?rlkey=cg5o780xvyjdepe74k750799q&raw=1> piglet
Reply by ●September 12, 20232023-09-12
On Tue, 12 Sep 2023 16:02:19 +0100, Piglet <erichpwagner@hotmail.com> wrote:>On 11/09/2023 15:16, John Larkin wrote: >> On Mon, 11 Sep 2023 08:50:54 -0400, Phil Hobbs >> <pcdhSpamMeSenseless@electrooptical.net> wrote: >> >>> On 2023-09-11 08:32, John Larkin wrote: >>>> On Mon, 11 Sep 2023 11:01:46 +0100, piglet <erichpwagner@hotmail.com> >>>> wrote: >>>> >>>>> On 11/09/2023 4:16 am, whit3rd wrote: >>>>>> On Sunday, September 10, 2023 at 12:55:12?PM UTC-7, John Smiht wrote: >>>>>>> On Sunday, September 10, 2023 at 7:57:03?AM UTC-5, Piglet wrote: >>>>>>>> On 06/09/2023 03:38, John Larkin wrote: >>>>>>>>> On Wed, 6 Sep 2023 02:31:04 -0000 (UTC), Phil Hobbs >>>>>>>>> <pcdhSpamM...@electrooptical.net> wrote: >>>>>>>>> >>>>>>>>>> John Larkin <jla...@highlandSNIPMEtechnology.com> wrote: >>>>>> >>>>>>>>>>>>> Now pull the base negative, through a current-limiting resistor. What >>>>>>>>>>>>> happens? >>>>>>>>>>>> >>>>>>>>>>>> Nothing until you exceed the emitter base reverse breakdown (or >>>>>>>>>>>> collector base breakdown) voltage, >>>>>>>>>>> >>>>>>>>>>> Not literally nothing, but not much interesting. It gets more >>>>>>>>>>> interesting when the base zeners. >>>>>>>>>>> >>>>>>>>>>>> >>>>>>>>>>>> Bitter-base is usually about 5V >>>>>>>>>>>> >>>>>>>>>>>> Behaves kind of like a zener diode and damages the transistor. >>>>>> >>>>>>>>>> Haven�t tried it, at least not on purpose, but I�d guess that when the >>>>>>>>>> avalanche starts, most of the electrons will get sucked up by the >>>>>>>>>> collector. >>>>>>>>>> >>>>>>>>>> Since it�s the electrons and not the holes that do the avalanching in >>>>>>>>>> silicon, that might partially suppress the avalanche. If that were true, >>>>>>>>>> putting a positive voltage on the collector would make the base voltage >>>>>>>>>> slightly more negative. >>>>>>>>>> >>>>>>>>>> Cheers >>>>>>>>>> >>>>>>>>>> Phil Hobbs >>>>>>>>> >>>>>>>>> I'd expect that zenering fills the b-e junction with lots of carriers, >>>>>>>>> and some find their way into the collector. I don't know how many. >>>>>>>>> >>>>>>>>> Probably a lot less than foward base current. >>>>>>>>> >>>>>>>>> I suppose I should try it. >>>>>>>>> >>>>>>>> Did you try it? I did today with a junk box NPN and results are kind of >>>>>>>> as expected: >>>>>>>> >>>>>>>> <https://www.dropbox.com/scl/fi/rqr7n3uunosswqhx4e59h/NPNunusualQuadrant.pdf?rlkey=6kcqwz3soawgxws2ouhbdktq3&raw=1> >>>>>> >>>>>>> Very good, Piglet. That is very linear which I did not expect. Your data results in >>>>>>> Ic(nA) = 9.2536Veb - 74.33 >>>>>> >>>>>> So, to expect this in future, should we assume the B-E breakdown creates light, and >>>>>> the collector current is a photodiode detecting that light? That does explain the >>>>>> effect, and predicts emitter current proportional to collector current. >>>>> >>>>> Yes, I think you meant collector current proportional to emitter >>>>> current? We did discusss all this back in 2015 under the thread "a very >>>>> silly circuit". About 25 years ago I think Stephen Woodward posted a >>>>> design idea in ED magazine using the effect to create a tiny negative >>>>> bias for opamp offset nulling in a positive rail only environment. >>>>> >>>>> piglet >>>> >>>> PV optocouplers are great for genereating a quiet floating voltage, >>>> but a transistor is cheaper. >>>> >>>> I guess a regular, transistor type optocoupler, will generate a >>>> floating voltage too. Something else to try. >>>> >>> >>> It will, but you have to accept an efficiency on the order of CTR/beta, >>> i.e. something below 0.1%. >> >> One could parallel the c-b and b-e junctions. Might help a little. >> >>> >>> Cheers >>> >>> Phil Hobbs >> >> OK for some tiny bias thing, probably not for running motors. >> >> This would be another curiosity measurement. You never know if such a >> thing might be useful some day. >> > >Here are some measurements I just made: > ><https://www.dropbox.com/scl/fi/jp7r2vkrqo8npkf2kws0t/OptoCoupler_PV.pdf?rlkey=cg5o780xvyjdepe74k750799q&raw=1> > >Seems bulk of the goodness comes from the C-B junction and paralleling >E+C makes hardly any difference.The photocurrent is driving the diode forward conduction curve, 60 mV per decade of current. Solar cells short themselves out.> >piglet >That's cool. I bet we'd see more voltage without the 1 meg resistors. One might pulse the LED hard at some low duty cycle and hang a cap on the output, to get more voltage. There must be a use for this! Opamp nulling has been suggested. I might have to design a multi-channel super-precise DC power source. This might fit in.
Reply by ●September 12, 20232023-09-12
On Tuesday, September 12, 2023 at 8:02:28 AM UTC-7, Piglet wrote:> On 11/09/2023 15:16, John Larkin wrote: > > On Mon, 11 Sep 2023 08:50:54 -0400, Phil Hobbs > > <pcdhSpamM...@electrooptical.net> wrote: > > > >> On 2023-09-11 08:32, John Larkin wrote:> >>> I guess a regular, transistor type optocoupler, will generate a > >>> floating voltage too. Something else to try.> >> It will, but you have to accept an efficiency on the order of CTR/beta, > >> i.e. something below 0.1%. > > > > One could parallel the c-b and b-e junctions. Might help a little.> Here are some measurements I just made: > > <https://www.dropbox.com/scl/fi/jp7r2vkrqo8npkf2kws0t/OptoCoupler_PV.pdf?rlkey=cg5o780xvyjdepe74k750799q&raw=1> > > Seems bulk of the goodness comes from the C-B junction and paralleling > E+C makes hardly any difference.That's expected; geometrically, the E is just a tiny dot, and an opaque one (heavy doping, nearly a conductor) and the collector is virtually the entire volume of the semiconductor die.
