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Started by Jan Panteltje September 29, 2012
Sometime ago I tried to make some low voltage oscillators, using JFETs.
I have now tried a large quantity of circuits, but this guy break the limits:
 http://www.dicks-website.eu/fetosc/enindex.htm

So anyways I copied his last circuit with BF245 JFETs, and with 2 JFETs
in parallel connected to a Conrad audio transformer, I get 2 Vpp at the gate with about 40 mV DC
supply in, enough to drive a power MOSFET like IRLZ34N I think.
 http://panteltje.com/pub/40_mV_oscillator_waveform_on_gate_2Vpp_IMG_3598.GIF
 http://panteltje.com/pub/40_mV_oscillator_IMG_3597.GIF

It perhaps opens up some possibility to use a .5 V solar cell directly with high efficiency.
Jan Panteltje wrote:
> Sometime ago I tried to make some low voltage oscillators, using JFETs. > I have now tried a large quantity of circuits, but this guy break the limits: > http://www.dicks-website.eu/fetosc/enindex.htm > > So anyways I copied his last circuit with BF245 JFETs, and with 2 JFETs > in parallel connected to a Conrad audio transformer, I get 2 Vpp at the gate with about 40 mV DC > supply in, enough to drive a power MOSFET like IRLZ34N I think. > http://panteltje.com/pub/40_mV_oscillator_waveform_on_gate_2Vpp_IMG_3598.GIF > http://panteltje.com/pub/40_mV_oscillator_IMG_3597.GIF > > It perhaps opens up some possibility to use a .5 V solar cell directly with high efficiency.
If you want to reliably get it started down to 300mV try the BF862 instead. -- Regards, Joerg http://www.analogconsultants.com/
On Sat, 29 Sep 2012 15:04:07 GMT, Jan Panteltje
<pNaonStpealmtje@yahoo.com> wrote:

>Sometime ago I tried to make some low voltage oscillators, using JFETs. >I have now tried a large quantity of circuits, but this guy break the limits: > http://www.dicks-website.eu/fetosc/enindex.htm > >So anyways I copied his last circuit with BF245 JFETs, and with 2 JFETs >in parallel connected to a Conrad audio transformer, I get 2 Vpp at the gate with about 40 mV DC >supply in, enough to drive a power MOSFET like IRLZ34N I think. > http://panteltje.com/pub/40_mV_oscillator_waveform_on_gate_2Vpp_IMG_3598.GIF > http://panteltje.com/pub/40_mV_oscillator_IMG_3597.GIF > >It perhaps opens up some possibility to use a .5 V solar cell directly with high efficiency.
A PHEMT would probably work at lower voltages than a jfet. -- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom timing and laser controllers Photonics and fiberoptic TTL data links VME analog, thermocouple, LVDT, synchro, tachometer Multichannel arbitrary waveform generators
On a sunny day (Sat, 29 Sep 2012 08:16:04 -0700) it happened Joerg
<invalid@invalid.invalid> wrote in <acohlrFfik6U1@mid.individual.net>:

>Jan Panteltje wrote: >> Sometime ago I tried to make some low voltage oscillators, using JFETs. >> I have now tried a large quantity of circuits, but this guy break the limits: >> http://www.dicks-website.eu/fetosc/enindex.htm >> >> So anyways I copied his last circuit with BF245 JFETs, and with 2 JFETs >> in parallel connected to a Conrad audio transformer, I get 2 Vpp at the gate with about 40 mV DC >> supply in, enough to drive a power MOSFET like IRLZ34N I think. >> http://panteltje.com/pub/40_mV_oscillator_waveform_on_gate_2Vpp_IMG_3598.GIF >> http://panteltje.com/pub/40_mV_oscillator_IMG_3597.GIF >> >> It perhaps opens up some possibility to use a .5 V solar cell directly with high efficiency. > > >If you want to reliably get it started down to 300mV try the BF862 instead.
??? It starts reliably at 40 mV now. :-) And I think I can get 20 mV for less.
Jan Panteltje wrote:
> On a sunny day (Sat, 29 Sep 2012 08:16:04 -0700) it happened Joerg > <invalid@invalid.invalid> wrote in <acohlrFfik6U1@mid.individual.net>: > >> Jan Panteltje wrote: >>> Sometime ago I tried to make some low voltage oscillators, using JFETs. >>> I have now tried a large quantity of circuits, but this guy break the limits: >>> http://www.dicks-website.eu/fetosc/enindex.htm >>> >>> So anyways I copied his last circuit with BF245 JFETs, and with 2 JFETs >>> in parallel connected to a Conrad audio transformer, I get 2 Vpp at the gate with about 40 mV DC >>> supply in, enough to drive a power MOSFET like IRLZ34N I think. >>> http://panteltje.com/pub/40_mV_oscillator_waveform_on_gate_2Vpp_IMG_3598.GIF >>> http://panteltje.com/pub/40_mV_oscillator_IMG_3597.GIF >>> >>> It perhaps opens up some possibility to use a .5 V solar cell directly with high efficiency. >> >> If you want to reliably get it started down to 300mV try the BF862 instead. > > ??? > It starts reliably at 40 mV now. > :-) > And I think I can get 20 mV for less.
How much power does it generate down there? Or is it just a science project? I found I could goose it to start really low, depends on how the voltage is connected (fast, sluggish, etc.). But that doesn't count as reliable. -- Regards, Joerg http://www.analogconsultants.com/
Jan Panteltje wrote:

> Sometime ago I tried to make some low voltage oscillators, using JFETs. > I have now tried a large quantity of circuits, but this guy break the limits: > http://www.dicks-website.eu/fetosc/enindex.htm > > So anyways I copied his last circuit with BF245 JFETs, and with 2 JFETs > in parallel connected to a Conrad audio transformer, I get 2 Vpp at the gate with about 40 mV DC > supply in, enough to drive a power MOSFET like IRLZ34N I think. > http://panteltje.com/pub/40_mV_oscillator_waveform_on_gate_2Vpp_IMG_3598.GIF > http://panteltje.com/pub/40_mV_oscillator_IMG_3597.GIF > > It perhaps opens up some possibility to use a .5 V solar cell directly with high efficiency.
Hmm, I looked at that, even tried that just now.. at least the one at the dicks_website with the transformer, I happen to have one sitting here. THe jfet I used has a pinch off of ~5v. All I see is ringing and if you wait it decays. Also after poking around with the scope, the gate is doing ~ 300mv ac. not even getting up to the gate voltage. Looking at it closer, I can see that it is using the Cgd to produce that ringing. strange beans. So I looked at that in LTspice, it shows a little different but it still decays. This reminds me of the induction eddy current heat treatment unit I updated for some one not to long ago. With that, I used heavy MOSFETS in a bridge to generate ringing of around 50k..60khz in the coil, which is the part that actually heats up the material. The effects look the same here. Jamie
On a sunny day (Sat, 29 Sep 2012 13:33:49 -0700) it happened Joerg
<invalid@invalid.invalid> wrote in <acp49jFk01bU1@mid.individual.net>:

>Jan Panteltje wrote: >> On a sunny day (Sat, 29 Sep 2012 08:16:04 -0700) it happened Joerg >> <invalid@invalid.invalid> wrote in <acohlrFfik6U1@mid.individual.net>: >> >>> Jan Panteltje wrote: >>>> Sometime ago I tried to make some low voltage oscillators, using JFETs. >>>> I have now tried a large quantity of circuits, but this guy break the limits: >>>> http://www.dicks-website.eu/fetosc/enindex.htm >>>> >>>> So anyways I copied his last circuit with BF245 JFETs, and with 2 JFETs >>>> in parallel connected to a Conrad audio transformer, I get 2 Vpp at the gate with about 40 mV DC >>>> supply in, enough to drive a power MOSFET like IRLZ34N I think. >>>> http://panteltje.com/pub/40_mV_oscillator_waveform_on_gate_2Vpp_IMG_3598.GIF >>>> http://panteltje.com/pub/40_mV_oscillator_IMG_3597.GIF >>>> >>>> It perhaps opens up some possibility to use a .5 V solar cell directly with high efficiency. >>> >>> If you want to reliably get it started down to 300mV try the BF862 instead. >> >> ??? >> It starts reliably at 40 mV now. >> :-) >> And I think I can get 20 mV for less. > > >How much power does it generate down there? Or is it just a science project? > >I found I could goose it to start really low, depends on how the voltage >is connected (fast, sluggish, etc.). But that doesn't count as reliable. > >-- >Regards, Joerg > >http://www.analogconsultants.com/
I suggest you actually READ dicks website as in the link above. And then, maybe read again what I wrote, that it can now easily drive a power MOSFET. With switching a power MOSFET with about .02 Ohm Rdson, from one of those thermocouple, you can get several amps for example, or from any other source.
On a sunny day (Sat, 29 Sep 2012 16:54:35 -0400) it happened Jamie
<jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote in
<Y0J9s.1800$4k1.467@newsfe18.iad>:

>Jan Panteltje wrote: > >> Sometime ago I tried to make some low voltage oscillators, using JFETs. >> I have now tried a large quantity of circuits, but this guy break the limits: >> http://www.dicks-website.eu/fetosc/enindex.htm >> >> So anyways I copied his last circuit with BF245 JFETs, and with 2 JFETs >> in parallel connected to a Conrad audio transformer, I get 2 Vpp at the gate with about 40 mV DC >> supply in, enough to drive a power MOSFET like IRLZ34N I think. >> http://panteltje.com/pub/40_mV_oscillator_waveform_on_gate_2Vpp_IMG_3598.GIF >> http://panteltje.com/pub/40_mV_oscillator_IMG_3597.GIF >> >> It perhaps opens up some possibility to use a .5 V solar cell directly with high efficiency. > >Hmm, > I looked at that, even tried that just now.. at least the one at the >dicks_website with the transformer, I happen to have one sitting here. > THe jfet I used has a pinch off of ~5v. > > All I see is ringing and if you wait it decays. Also after poking >around with the scope, the gate is doing ~ 300mv ac. not even getting up >to the gate voltage. > > Looking at it closer, I can see that it is using the Cgd to produce >that ringing. strange beans. > > So I looked at that in LTspice, it shows a little different but it >still decays. > > This reminds me of the induction eddy current heat treatment unit I >updated for some one not to long ago. With that, I used heavy MOSFETS in >a bridge to generate ringing of around 50k..60khz in the coil, which is >the part that actually heats up the material. The effects look the same >here. > >Jamie
Well you must be doing something wrong, or defective part perhaps. I have a steady 2Vpp sine at the gate with 42 mV or so in, 2 BF245 parallel. Today I have planned to wind my own transformer, and 'up' the turns ratio a bit. I have plans :-) Do not forget to decouple that mV supply!
Jan Panteltje wrote:
> On a sunny day (Sat, 29 Sep 2012 13:33:49 -0700) it happened Joerg > <invalid@invalid.invalid> wrote in <acp49jFk01bU1@mid.individual.net>: > >> Jan Panteltje wrote: >>> On a sunny day (Sat, 29 Sep 2012 08:16:04 -0700) it happened Joerg >>> <invalid@invalid.invalid> wrote in <acohlrFfik6U1@mid.individual.net>: >>> >>>> Jan Panteltje wrote: >>>>> Sometime ago I tried to make some low voltage oscillators, using JFETs. >>>>> I have now tried a large quantity of circuits, but this guy break the limits: >>>>> http://www.dicks-website.eu/fetosc/enindex.htm >>>>> >>>>> So anyways I copied his last circuit with BF245 JFETs, and with 2 JFETs >>>>> in parallel connected to a Conrad audio transformer, I get 2 Vpp at the gate with about 40 mV DC >>>>> supply in, enough to drive a power MOSFET like IRLZ34N I think. >>>>> http://panteltje.com/pub/40_mV_oscillator_waveform_on_gate_2Vpp_IMG_3598.GIF >>>>> http://panteltje.com/pub/40_mV_oscillator_IMG_3597.GIF >>>>> >>>>> It perhaps opens up some possibility to use a .5 V solar cell directly with high efficiency. >>>> If you want to reliably get it started down to 300mV try the BF862 instead. >>> ??? >>> It starts reliably at 40 mV now. >>> :-) >>> And I think I can get 20 mV for less. >> >> How much power does it generate down there? Or is it just a science project? >> >> I found I could goose it to start really low, depends on how the voltage >> is connected (fast, sluggish, etc.). But that doesn't count as reliable. >> >> -- >> Regards, Joerg >> >> http://www.analogconsultants.com/ > > I suggest you actually READ dicks website as in the link above. > > And then, maybe read again what I wrote, that it can now easily drive a power MOSFET. > With switching a power MOSFET with about .02 Ohm Rdson, > from one of those thermocouple, you can get several amps for example, > or from any other source.
And what useful piece of equipment did you power from it? -- Regards, Joerg http://www.analogconsultants.com/
Jan Panteltje wrote:
> On a sunny day (Sat, 29 Sep 2012 16:54:35 -0400) it happened Jamie > <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote in > <Y0J9s.1800$4k1.467@newsfe18.iad>: > > >>Jan Panteltje wrote: >> >> >>>Sometime ago I tried to make some low voltage oscillators, using JFETs. >>>I have now tried a large quantity of circuits, but this guy break the limits: >>> http://www.dicks-website.eu/fetosc/enindex.htm >>> >>>So anyways I copied his last circuit with BF245 JFETs, and with 2 JFETs >>>in parallel connected to a Conrad audio transformer, I get 2 Vpp at the gate with about 40 mV DC >>>supply in, enough to drive a power MOSFET like IRLZ34N I think. >>> http://panteltje.com/pub/40_mV_oscillator_waveform_on_gate_2Vpp_IMG_3598.GIF >>> http://panteltje.com/pub/40_mV_oscillator_IMG_3597.GIF >>> >>>It perhaps opens up some possibility to use a .5 V solar cell directly with high efficiency. >> >>Hmm, >> I looked at that, even tried that just now.. at least the one at the >>dicks_website with the transformer, I happen to have one sitting here. >> THe jfet I used has a pinch off of ~5v. >> >> All I see is ringing and if you wait it decays. Also after poking >>around with the scope, the gate is doing ~ 300mv ac. not even getting up >>to the gate voltage. >> >> Looking at it closer, I can see that it is using the Cgd to produce >>that ringing. strange beans. >> >> So I looked at that in LTspice, it shows a little different but it >>still decays. >> >> This reminds me of the induction eddy current heat treatment unit I >>updated for some one not to long ago. With that, I used heavy MOSFETS in >>a bridge to generate ringing of around 50k..60khz in the coil, which is >>the part that actually heats up the material. The effects look the same >>here. >> >>Jamie > > > Well you must be doing something wrong, or defective part perhaps. > I have a steady 2Vpp sine at the gate with 42 mV or so in, 2 BF245 parallel. > Today I have planned to wind my own transformer, and 'up' the turns ratio a bit. > I have plans :-) > > Do not forget to decouple that mV supply!
Well maybe but, I have that transformer and the best I get is ~ 300mv at the gate, it's not even pinching off the unit. I hunt around for a different fet with lower threshold. Jamie