On Thu, 21 Sep 2023 05:24:34 GMT, Jan Panteltje <alien@comet.invalid> wrote:>On a sunny day (Wed, 20 Sep 2023 21:28:49 -0700 (PDT)) it happened amal >banerjee <dakupoto@gmail.com> wrote in ><21592d6c-93a9-4852-a6d9-285c75bbd202n@googlegroups.com>: > >>On Wednesday, September 20, 2023 at 8:51:50 PM UTC+5:30, John Larki= >>n wrote: >>> On Wed, 20 Sep 2023 08:08:08 -0700 (PDT), amal banerjee >>> <daku...@gmail.com> wrote: >>> >>> >Could some electronics guru please help ? I am looking for a very low(fe= >>w milliVolts) VTO commercially available NMOS, and its corresponding PMOS.= >> >>> >I am trying to use a reverse biased photodiode(very low output current) = >>to >>> >trigger a PMOS. The output voltage could then be used to trigger ideally= >> a >>> >BJT. Any hints, suggestiosn would be greatly appreciated. Thanks in adva= >>nce. >>> What is VTO? >>> >>> I don't think such a part exists. A photodiode might just barely turn >>> on a high-beta bipolar transisor. >>> >>> What's the open-circuit voltage of the photodiode? What's the current? >>> Is a power supply available? If the pd is back-biased by a supply, >>> you'd have lots of voltage available to turn on a mosfet. >>> >>> A lithium battery might power a micropower comparator for decades. >> >>Sorry for the confusion. 'VTO' means threshold voltage for the mosfet. >>The candidate photodiode is BPW31|34. The datasheet contains the following= >> >>data: >>Open circuit voltage : 440 mV >>In reverse bias, the diode is open circuit, so current should flow. The da= >>rk current >>is 12 pA. > >Think 'current' >the reverse photo-diode could drive the base of for exampe a NPN directly >photo diode current amplified by beta * R1 is output. >Note leakage etc.. > > ------------------------ + > | | >--- R1 a few k >/ \ | >--- |------------ out, negative going on light input > | c > ---- b NPN beta 200 > e > | > ----------------- GNDOr drive a logic-level mosfet. Add a gate-source resistor. One might get 440 mV using the pd in photovoltaic mode, but it will make many volts in reverse-bias mode.> ------------------------ + > | | >--- R1 a few k >/ \ | > | |------------ out, negative going on light input > | d > |----g nfet > | s >R9 | > | ----------------- GNDMeasure the pd current when illuminated and pick R9 suitably.
Looking for very low threshold voltage NMOS and its PMOS counterpart
Started by ●September 20, 2023
Reply by ●September 21, 20232023-09-21
Reply by ●September 21, 20232023-09-21
On Wed, 20 Sep 2023 08:08:08 -0700 (PDT), amal banerjee <dakupoto@gmail.com> wrote:>Could some electronics guru please help ? I am looking for a very low(few milliVolts) VTO commercially available NMOS, and its corresponding PMOS. >I am trying to use a reverse biased photodiode(very low output current) to >trigger a PMOS. The output voltage could then be used to trigger ideally a >BJT. Any hints, suggestiosn would be greatly appreciated. Thanks in advance.Advanced Linear Devices make mos discretes with turn-on voltages dialable down to zero. http://www.aldinc.com/ RL
Reply by ●September 22, 20232023-09-22
On Thursday, September 21, 2023 at 10:54:43 AM UTC+5:30, Jan Panteltje wrote:> On a sunny day (Wed, 20 Sep 2023 21:28:49 -0700 (PDT)) it happened amal > banerjee <daku...@gmail.com> wrote in > <21592d6c-93a9-4852...@googlegroups.com>: > > >On Wednesday, September 20, 2023 at 8:51:50 PM UTC+5:30, John Larki= > >n wrote: > >> On Wed, 20 Sep 2023 08:08:08 -0700 (PDT), amal banerjee > >> <daku...@gmail.com> wrote: > >> > >> >Could some electronics guru please help ? I am looking for a very low(fe= > >w milliVolts) VTO commercially available NMOS, and its corresponding PMOS.= > > > >> >I am trying to use a reverse biased photodiode(very low output current) = > >to > >> >trigger a PMOS. The output voltage could then be used to trigger ideally= > > a > >> >BJT. Any hints, suggestiosn would be greatly appreciated. Thanks in adva= > >nce. > >> What is VTO? > >> > >> I don't think such a part exists. A photodiode might just barely turn > >> on a high-beta bipolar transisor. > >> > >> What's the open-circuit voltage of the photodiode? What's the current? > >> Is a power supply available? If the pd is back-biased by a supply, > >> you'd have lots of voltage available to turn on a mosfet. > >> > >> A lithium battery might power a micropower comparator for decades. > > > >Sorry for the confusion. 'VTO' means threshold voltage for the mosfet. > >The candidate photodiode is BPW31|34. The datasheet contains the following= > > > >data: > >Open circuit voltage : 440 mV > >In reverse bias, the diode is open circuit, so current should flow. The da= > >rk current > >is 12 pA. > > Think 'current' > the reverse photo-diode could drive the base of for exampe a NPN directly > photo diode current amplified by beta * R1 is output. > Note leakage etc.. > > ------------------------ + > | | > --- R1 a few k > / \ | > --- |------------ out, negative going on light input > | c > ---- b NPN beta 200 > e > | > ----------------- GNDI have tested your suggestion with SPICE simulations using an ordinary BJT(BC547) and two RF BJTs (BFR92A, BFQ790) each biased(as per Vce, Ic values listed in their respective datasheets) for beta values(150-200). I am using a GaAs photodiode SPICE model, which uses a third input node for an input voltage for the incident light. The light is pulsed, @ 1.5 MHz, 15.0 MHz and 150.0 MHz with pulse amplitudes in the low milliVolt(1-2) range. Of the three transistors BFQ790 performs best, but like each of the other two, the output voltage at the output 50.0 Ohm resistor is in the tenths of milliVolt range.
Reply by ●September 22, 20232023-09-22
On Thursday, September 21, 2023 at 7:45:16 PM UTC+5:30, John Larkin wrote:> On Thu, 21 Sep 2023 05:24:34 GMT, Jan Panteltje <al...@comet.invalid> > wrote: > >On a sunny day (Wed, 20 Sep 2023 21:28:49 -0700 (PDT)) it happened amal > >banerjee <daku...@gmail.com> wrote in > ><21592d6c-93a9-4852...@googlegroups.com>: > > > >>On Wednesday, September 20, 2023 at 8:51:50 PM UTC+5:30, John Larki= > >>n wrote: > >>> On Wed, 20 Sep 2023 08:08:08 -0700 (PDT), amal banerjee > >>> <daku...@gmail.com> wrote: > >>> > >>> >Could some electronics guru please help ? I am looking for a very low(fe= > >>w milliVolts) VTO commercially available NMOS, and its corresponding PMOS.= > >> > >>> >I am trying to use a reverse biased photodiode(very low output current) = > >>to > >>> >trigger a PMOS. The output voltage could then be used to trigger ideally= > >> a > >>> >BJT. Any hints, suggestiosn would be greatly appreciated. Thanks in adva= > >>nce. > >>> What is VTO? > >>> > >>> I don't think such a part exists. A photodiode might just barely turn > >>> on a high-beta bipolar transisor. > >>> > >>> What's the open-circuit voltage of the photodiode? What's the current? > >>> Is a power supply available? If the pd is back-biased by a supply, > >>> you'd have lots of voltage available to turn on a mosfet. > >>> > >>> A lithium battery might power a micropower comparator for decades. > >> > >>Sorry for the confusion. 'VTO' means threshold voltage for the mosfet. > >>The candidate photodiode is BPW31|34. The datasheet contains the following= > >> > >>data: > >>Open circuit voltage : 440 mV > >>In reverse bias, the diode is open circuit, so current should flow. The da= > >>rk current > >>is 12 pA. > > > >Think 'current' > >the reverse photo-diode could drive the base of for exampe a NPN directly > >photo diode current amplified by beta * R1 is output. > >Note leakage etc.. > > > > ------------------------ + > > | | > >--- R1 a few k > >/ \ | > >--- |------------ out, negative going on light input > > | c > > ---- b NPN beta 200 > > e > > | > > ----------------- GND > Or drive a logic-level mosfet. Add a gate-source resistor. > > One might get 440 mV using the pd in photovoltaic mode, but it will > make many volts in reverse-bias mode. > > ------------------------ + > > | | > >--- R1 a few k > >/ \ | > > | |------------ out, negative going on light input > > | d > > |----g nfet > > | s > >R9 | > > | ----------------- GND > > Measure the pd current when illuminated and pick R9 suitably.I agree that logic level mosfets might be best. I did a SPICE simulation with BSIM 4.8.2 level=54 NMOS-PMOS pair for an inverter. Even without a gate-source resistor, the output was 150.0 - 200 mV range for pulsed input to my GaAs photodiode model(please check my previous response to Jan's message). The pulses were at 1.5, 15 and 150 MHz respectively.
Reply by ●September 22, 20232023-09-22
On Thursday, September 21, 2023 at 8:17:31 AM UTC-7, legg wrote:> On Wed, 20 Sep 2023 08:08:08 -0700 (PDT), amal banerjee > <daku...@gmail.com> wrote: > >Could some electronics guru please help ? I am looking for a very low(few milliVolts) VTO commercially available NMOS, and its corresponding PMOS. > >I am trying to use a reverse biased photodiode(very low output current) to > >trigger a PMOS. The output voltage could then be used to trigger ideally a > >BJT. Any hints, suggestiosn would be greatly appreciated. Thanks in advance. > Advanced Linear Devices make mos discretes with turn-on voltages > dialable down to zero. > > http://www.aldinc.com/Yes, but the turn-on is trimmed, not made abrupt, so 'down to zero' is more of a gain specification than a full switch threshold. JFETs have been available for zero-threshold for years, and were quite useful for low-leakage input applications.
Reply by ●September 22, 20232023-09-22
On a sunny day (Thu, 21 Sep 2023 23:20:09 -0700 (PDT)) it happened amal banerjee <dakupoto@gmail.com> wrote in <e1f8fc46-a40d-4fb8-beda-bd960b476c44n@googlegroups.com>:>On Thursday, September 21, 2023 at 10:54:43 AM UTC+5:30, Jan Pantel= >tje wrote: >> On a sunny day (Wed, 20 Sep 2023 21:28:49 -0700 (PDT)) it happened amal= > >> banerjee <daku...@gmail.com> wrote in >> <21592d6c-93a9-4852...@googlegroups.com>: >> >> >On Wednesday, September 20, 2023 at 8:51:50 PM UTC+5:30, John La= >rki= >> >n wrote: >> >> On Wed, 20 Sep 2023 08:08:08 -0700 (PDT), amal banerjee >> >> <daku...@gmail.com> wrote: >> >> >> >> >Could some electronics guru please help ? I am looking for a very low= >(fe= >> >w milliVolts) VTO commercially available NMOS, and its corresponding PMO= >S.= >> > >> >> >I am trying to use a reverse biased photodiode(very low output curren= >t) = >> >to >> >> >trigger a PMOS. The output voltage could then be used to trigger idea= >lly= >> > a >> >> >BJT. Any hints, suggestiosn would be greatly appreciated. Thanks in a= >dva= >> >nce. >> >> What is VTO? >> >> >> >> I don't think such a part exists. A photodiode might just barely turn= > >> >> on a high-beta bipolar transisor. >> >> >> >> What's the open-circuit voltage of the photodiode? What's the current?= > >> >> Is a power supply available? If the pd is back-biased by a supply, >> >> you'd have lots of voltage available to turn on a mosfet. >> >> >> >> A lithium battery might power a micropower comparator for decades. >> > >> >Sorry for the confusion. 'VTO' means threshold voltage for the mosfet. >> >The candidate photodiode is BPW31|34. The datasheet contains the followi= >ng= >> > >> >data: >> >Open circuit voltage : 440 mV >> >In reverse bias, the diode is open circuit, so current should flow. The = >da= >> >rk current >> >is 12 pA. >> >> Think 'current' >> the reverse photo-diode could drive the base of for exampe a NPN directly= > >> photo diode current amplified by beta * R1 is output. >> Note leakage etc.. >> >> ------------------------ + >> | | >> --- R1 a few k >> / \ | >> --- |------------ out, negative going on light input >> | c >> ---- b NPN beta 200 >> e >> | >> ----------------- GND >I have tested your suggestion with SPICE simulations using an ordinary BJT(= >BC547) and two RF BJTs >(BFR92A, BFQ790) each biased(as per Vce, Ic values listed in their respecti= >ve datasheets) for beta >values(150-200). I am using a GaAs photodiode SPICE model, which uses a thi= >rd input node for an >input voltage for the incident light. The light is pulsed, @ 1.5 MHz, 15.0 = >MHz and 150.0 MHz with pulse >amplitudes in the low milliVolt(1-2) range. Of the three transistors BFQ790= > performs best, but like each >of the other two, the output voltage at the output 50.0 Ohm resistor is in = >the tenths of milliVolt range.R1 is supposed to be several k, 100 k would be a good start Add an emitter follower if you want to drive 50 Ohms You could also use a darlington configuration in place of the first tranistor to mutiply beta / current gain to say 200 x 200 So the 'heavy' version: ------------------------------------- + | | | | --- | R1 100 k | / \ | | c --- | |--zener---b NPN TR3 | c TR1 | | e -- b NPN c | |-----> out, negative going on light input e -------- b NPN | | darlington e TR2 R3 R2 50 Ohm | | | ----------------- GND You could add a few volt zener in the base of TR3 to lower DC level output for no signal. So for say 12 V supply drop the base of TR3 for no signal to about 1V. The possibilities are endless. Darlington for TR3 will let you output even more Yes, your 150 MHz... is bit high for those transistors.. won't work. Maybe a BFY90 in darlington mode with R1 220 Ohm will? Not tested. Or triple darlington.... What is the photo diode reverse current with light on say a 12V supply?
Reply by ●September 22, 20232023-09-22
On Wednesday, September 20, 2023 at 8:08:14 AM UTC-7, amal banerjee wrote:> Could some electronics guru please help ? I am looking for a very low(few milliVolts) VTO commercially available NMOS, and its corresponding PMOS. > I am trying to use a reverse biased photodiode(very low output current) to > trigger a PMOS. The output voltage could then be used to trigger ideally a > BJT. Any hints, suggestiosn would be greatly appreciated. Thanks in advance.Your signal (a photocurrent) is fast? And you want to switch according to that current? There's very little voltage gain in a single MOS device, and what you want might be to avoid current lost to charging the photodiode stray capacitance (i.e. you want near-zero dV/dt); a good receiver for a photodiode with low current output is an op amp with resistor negative feedback, i.e. a transimpedance amplifier. That way, there's negligible delta-V.
Reply by ●September 22, 20232023-09-22
amal banerjee <dakupoto@gmail.com> wrote:> On Thursday, September 21, 2023 at 10:54:43/AM UTC+5:30, Jan Panteltje wrote: >> On a sunny day (Wed, 20 Sep 2023 21:28:49 -0700 (PDT)) it happened amal >> banerjee <daku...@gmail.com> wrote in >> <21592d6c-93a9-4852...@googlegroups.com>: >> >>> On Wednesday, September 20, 2023 at 8:51:50/PM UTC+5:30, John Larki> >n wrote: >>>> On Wed, 20 Sep 2023 08:08:08 -0700 (PDT), amal banerjee >>>> <daku...@gmail.com> wrote: >>>> >>>>> Could some electronics guru please help ? I am looking for a very low(fe= >>> w milliVolts) VTO commercially available NMOS, and its corresponding PMOS.= >>> >>>>> I am trying to use a reverse biased photodiode(very low output current) = >>> to >>>>> trigger a PMOS. The output voltage could then be used to trigger ideally= >>> a >>>>> BJT. Any hints, suggestiosn would be greatly appreciated. Thanks in adva> >nce. >>>> What is VTO? >>>> >>>> I don't think such a part exists. A photodiode might just barely turn >>>> on a high-beta bipolar transisor. >>>> >>>> What's the open-circuit voltage of the photodiode? What's the current? >>>> Is a power supply available? If the pd is back-biased by a supply, >>>> you'd have lots of voltage available to turn on a mosfet. >>>> >>>> A lithium battery might power a micropower comparator for decades. >>> >>> Sorry for the confusion. 'VTO' means threshold voltage for the mosfet. >>> The candidate photodiode is BPW31|34. The datasheet contains the following> > >>> data: >>> Open circuit voltage : 440 mV >>> In reverse bias, the diode is open circuit, so current should flow. The da= >>> rk current >>> is 12 pA. >> >> Think 'current' >> the reverse photo-diode could drive the base of for exampe a NPN directly >> photo diode current amplified by beta * R1 is output. >> Note leakage etc.. >> >> ------------------------ + >> | | >> --- R1 a few k >> / \ | >> --- |------------ out, negative going on light input >> | c >> ---- b NPN beta 200 >> e >> | >> ----------------- GND > I have tested your suggestion with SPICE simulations using an ordinary > BJT(BC547) and two RF BJTs > (BFR92A, BFQ790) each biased(as per Vce, Ic values listed in their > respective datasheets) for beta > values(150-200). I am using a GaAs photodiode SPICE model, which uses a > third input node for an > input voltage for the incident light. The light is pulsed, @ 1.5 MHz, > 15.0 MHz and 150.0 MHz with pulse > amplitudes in the low milliVolt(1-2) range. Of the three transistors > BFQ790 performs best, but like each > of the other two, the output voltage at the output 50.0 Ohm resistor is > in the tenths of milliVolt range. >If you don’t know how much light you’ve got, you’re probably doomed. That needs to be in optical terms, like “1.2 ns full width at half maximum, 1-2 picojoules, 950 nm”. It also matters whether the light is spatially coherent, because that governs how small a photodiode you can use. If you tell us what you’re actually trying to do, we can be a lot more helpful. Generating a sync signal from a laser beam is much easier than detecting scattered light from a matte-textured object at a distance, but there are tricks to make both easier. Something like, “I need to detect laser pulses bouncing off a microscope sample so that I can do lock-in measurements of the photoacoustic response” or “I’m going to bounce laser pulses off my cat” would help a lot. Cheers Phil Hobbs Cheers Phil Hobbs For instance Find that out, first -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics
Reply by ●September 22, 20232023-09-22
On Thu, 21 Sep 2023 23:28:56 -0700 (PDT), amal banerjee <dakupoto@gmail.com> wrote:>On Thursday, September 21, 2023 at 7:45:16?PM UTC+5:30, John Larkin wrote: >> On Thu, 21 Sep 2023 05:24:34 GMT, Jan Panteltje <al...@comet.invalid> >> wrote: >> >On a sunny day (Wed, 20 Sep 2023 21:28:49 -0700 (PDT)) it happened amal >> >banerjee <daku...@gmail.com> wrote in >> ><21592d6c-93a9-4852...@googlegroups.com>: >> > >> >>On Wednesday, September 20, 2023 at 8:51:50?PM UTC+5:30, John Larki= >> >>n wrote: >> >>> On Wed, 20 Sep 2023 08:08:08 -0700 (PDT), amal banerjee >> >>> <daku...@gmail.com> wrote: >> >>> >> >>> >Could some electronics guru please help ? I am looking for a very low(fe= >> >>w milliVolts) VTO commercially available NMOS, and its corresponding PMOS.= >> >> >> >>> >I am trying to use a reverse biased photodiode(very low output current) = >> >>to >> >>> >trigger a PMOS. The output voltage could then be used to trigger ideally= >> >> a >> >>> >BJT. Any hints, suggestiosn would be greatly appreciated. Thanks in adva= >> >>nce. >> >>> What is VTO? >> >>> >> >>> I don't think such a part exists. A photodiode might just barely turn >> >>> on a high-beta bipolar transisor. >> >>> >> >>> What's the open-circuit voltage of the photodiode? What's the current? >> >>> Is a power supply available? If the pd is back-biased by a supply, >> >>> you'd have lots of voltage available to turn on a mosfet. >> >>> >> >>> A lithium battery might power a micropower comparator for decades. >> >> >> >>Sorry for the confusion. 'VTO' means threshold voltage for the mosfet. >> >>The candidate photodiode is BPW31|34. The datasheet contains the following= >> >> >> >>data: >> >>Open circuit voltage : 440 mV >> >>In reverse bias, the diode is open circuit, so current should flow. The da= >> >>rk current >> >>is 12 pA. >> > >> >Think 'current' >> >the reverse photo-diode could drive the base of for exampe a NPN directly >> >photo diode current amplified by beta * R1 is output. >> >Note leakage etc.. >> > >> > ------------------------ + >> > | | >> >--- R1 a few k >> >/ \ | >> >--- |------------ out, negative going on light input >> > | c >> > ---- b NPN beta 200 >> > e >> > | >> > ----------------- GND >> Or drive a logic-level mosfet. Add a gate-source resistor. >> >> One might get 440 mV using the pd in photovoltaic mode, but it will >> make many volts in reverse-bias mode. >> > ------------------------ + >> > | | >> >--- R1 a few k >> >/ \ | >> > | |------------ out, negative going on light input >> > | d >> > |----g nfet >> > | s >> >R9 | >> > | ----------------- GND >> >> Measure the pd current when illuminated and pick R9 suitably. >I agree that logic level mosfets might be best. I did a SPICE simulation with BSIM 4.8.2 level=54 >NMOS-PMOS pair for an inverter. Even without a gate-source resistor, the output was 150.0 - 200 mV >range for pulsed input to my GaAs photodiode model(please check my previous response to Jan's >message). The pulses were at 1.5, 15 and 150 MHz respectively.I don't understand this. What photodiode are you using? What's the optical pulse width?
Reply by ●September 22, 20232023-09-22
On Friday, September 22, 2023 at 2:47:37 PM UTC+5:30, whit3rd wrote:> On Wednesday, September 20, 2023 at 8:08:14 AM UTC-7, amal banerjee wrote: > > Could some electronics guru please help ? I am looking for a very low(few milliVolts) VTO commercially available NMOS, and its corresponding PMOS. > > I am trying to use a reverse biased photodiode(very low output current) to > > trigger a PMOS. The output voltage could then be used to trigger ideally a > > BJT. Any hints, suggestiosn would be greatly appreciated. Thanks in advance. > Your signal (a photocurrent) is fast? And you want to switch according to that current? > > There's very little voltage gain in a single MOS device, and what you want might be to avoid current lost to > charging the photodiode stray capacitance (i.e. you want near-zero dV/dt); a good receiver for a photodiode > with low current output is an op amp with resistor negative feedback, i.e. a transimpedance amplifier. > That way, there's negligible delta-V.Totally in agreement about the op-amp transimpedance amplifier. However, the gain-bandwidth-product of even high end op-amps certainly would not extend beyond some 10s of MHz.
