Good stuff mr. Ilett, thank you! So many times you've provided the missing link between [basic] and [difficult] theory simply by spending time on understanding it and then explaining it with your own angle. Assembly language, MosFETs and now JFETs. Excellent stuff! Of course it's your own prerogative to make whatever videos you'd like, but if you are unsure maybe a survey like Dave Jones did could be helpful? I'd vote for this kind of stuff. And finishing the Muppet.
Absolutely LOVE this! ❤ I've been using 2N3819s quite a lot lately but I was curious about symmetrical JFETs, also. I'd also like to ask, Julian, if the solder less breadboard is made by Lego? Gr8 upload, very enlightening easy for me to follow. Thanks. 🙂
If you ever get back to playing with JFETS try the MPF102 she is highly sensitive, I have been building stand alone ghost detectors with these JFETS for some time now, they are very simple consisting of the JFET, an LED and if you wish to extend the antenna, solder on a 1 meg resistor. I didn't have one on had the other day, but needed to get one out the door for a ghost-buster outfit, so I soldered on a 1k ohm resistor, worked as well as the 1 meg, in fact I think it was a bit more sensitive. These little units can detect a fellow combing his hair two rooms away on a dry day, The way I build them is quit simple on a 9 volt plug with the skin removed, solder the Gate to the + terminal, the source through the LED to the - terminal, the Drain works as the antenna and is where to attach the resistor to extend the range. To use, simply hook it up to a fresh 9 volt battery and keep an eye on the LED, it will pick up any negative voltage flux within a room or two. I have three of them that I built using different methods, the second one is built on the same basis but using a plastic enclosure and having the works hidden as well as a toggle switch to add to the professional look. I have a few other type I have put to gather, one based on an Arduino to read the voltage and light up LEDs depending on strength, from one LED to 10 for full force. Another I built following Big CLive's video but instead of using rabbit ears, which I could not find in our small town, insted I mounted her on a project board, then used a couple of pieces of heavy copper wire recovered from an old Power Supply These things are great fun!
Thanks Julian, for a nice introductory video. The reason why doping levels are so low is because a Silicon crystal with a small number of imperfections is required, rather than a Phosphorous or Boron (etc) crystal with Silicon imperfections. More than the minutest amount of imperfection is first of all overkill, and second far too disruptive of the Silicon lattice. Interestingly, it could take us days at temperatures between 950°C and 1275° C under extremely clean conditions to create those small doping levels. The diffusion process occurs very slowly, and a combination of dopant flow through the ovens, plus temperature and time control, allows for quite precise control of layer thicknesses, junction depths. (Wafer fabrication doesn't adhere to a normal working day!) This is one reason why CPU's, GPU's, and the like, are so expensive; there are a number of different dopant layers, and several intermediate cleaning and preparation procedures for each layer in the Silicon, each of which can take from hours to a number of days. One power outage can mean the loss of a number of batches of devices, each at different stages of manufacture. Chip yields, initial testing, selecting, packaging and re-testing also affect the factory prices.
Nice. About those breadboards and the base plate, I've never seen such, what is the manufacturer and are there any more different modules to that system?
It's always awesome to see a video that just came out on a topic that I've been currently researching. By the way, where did you purchase those transistors from? Are there any good stores you would recommend depending on the country you're in? Thanks for posting this! And Happy New Year.
im just getting into electronics and im really enjoying it so far. i bought a strip of those MMBJ201 SMD and a pcb adapter board . im using them to act as the tubes in a marshal Plexi amp but in a pedal form and they sound really good. really good dynamics . if i pick my guitar softly its completely clean sounding no distortion, if i hit my strings a little bit harder it starts to break up with some distortion in a really nice sounding way. i very much enjoyed your video on these Jfets id like to learn more about all my transistors .
Ah, a drop of the good stuff. Technical investigations and explanations, the reason I subbed in the first place. Will this progress through into a practical application? You've got some other great projects on the go.
When you bring the gate positive w.r.t. source, it matters how much. If you bring it more than 0.6V (one diode fwd drop), you are actually injecting significant current through the gate. If you bring it e.g. at 0.3V, you are basically only enhancing the channel (as you do not yet have significant current through the diode). So the question regarding your setup is are you enhancing the channel or also pushing current through that diode?
That looks really interesting. Now I'm a bit confused because there are op-amps with JFET inputs (like TL07x) to get higher input impedance, among other things. But from what you shown it seems like the leakage current is really high, compared to regular BJTs..
I've seen JFET circuits with "100 Meg" gate resistors made out of leaky reversed biased transistors... pretty sensitive stuff. See the inputs of the TL072 JFET op amp. J112s make really good electric guitar buffer/signal boosters for use in the signal chain in front of other effects devices. 2N5457 is good too and J201 has much lower gain. Jerry Garcia's guitar had a 2N5457 based signal booster IIRC. You'll find lots of great JFET experimentation at DIY guitar effects sites like www.diystompboxes.com/smfforum/ Happy New Year!
@Julian reverse the polarity of the battery and of the LED in the circuit, then you can pull the gate fully down. Running the circuit in the opposite direction essentially switching between blocking and enhance modes?
On thhe subject of JFETs, you should do a video on lambda diodes. It's basically just a P type and N type jfet in series and has an operational region with negative resistance. Sort of like a tunnel diode, but higher voltage.
Interesting little devices these are. I work with vacuum tubes mostly but I greatly appreciate more modern solutions. Power consumption and size of devices made today would have been thought as impossible 50 years ago.
Hello, Julian... I'm big fun of your videos, howether I'm complete amateur... What you showed us here amazed me. i know, I'm noob. But, I have one very important question for you. I'm sure it's possible, but I have no idea how to make it on breadboar, so... If you don't mind? Is this possible to boost transistor reaction, so it could "feel" my finger from, let's say 5cms away or 10cms? I will play for sure with yourdemonstration, but my idea is to use the transistor to react on eletro-magnetic field (let's say 5cm) and then digitally use it as a bit (I guess another transistor could help me to turn 5V on when transistors is "in range"). Yeah, I will be reading and trying... My idea is to have two or three such transistors generating digital answers and the difference in time (small changes in time (measuread by simple timer) - should allow me to use these transistors for "simpliest radar"... Simply - if I know which transistor is closest to magnetic field - I know where is the source of the field... Well, maybe my sci-fi idea, I'm complete amateur, but I'm working on something, right know it's a software simulation, but I want to build it in breadboard first and then... I hope to build something very simple and very amazin - I must say. Have a good day!
You can build a complete E-field detector on the top of an upright 9v batt. (which is the power source) that will last for years, which will tell all sorts of things about the E-field (esp.in cold dry weather). On my bench, I have a large sheet of black conductive foam connected to earth ground. It has saved me many circuit components!!! often (VERY) when you sit at your workbench, and the LED glows bright--you need to touch the foam--sometimes the shock actually HURTS!! I have learned to make a fist and discharge the static through a tight-skinned knuckle. Or, better yet, tightly hold a small (somewhat long ~6") conducting rod and touch the other end to the foam--A VISIBLE DISCHARGE, BUT NO SHOCK AT ALL!!! Again, this can be spectacular in very cool dry weather. --dalE
How to make +-12V supply from a single 1A 12v wallwart? In my Behringer Neutron the PSU is working from this little 12v wallwart. Is that some kind of inverting IC or it can be simpler?
Had a lot of fun with 2N3819's about 40 years ago...Leave the gate disconnected, then comb my hair nearby. (Also with a small lamp - LED'S too expensive then) and watch it flash, dim, go off as I moved to and fro the work desk. The IGFET (Dual-gate) 40673 was a different kettle of fish! If one removed the ring shorting everything together before it was in-circuit, it was TOAST!
Those 40673's were so fragile! I fried a couple by desoldering them from a circuit, before reading the handling instructions. Later devices had internally-constructed protective diodes, which would allow for a little mishandling.
Happy New Year Julian. Some time ago you showed a fake LM2596HV going up in smoke. I noticed you powered it with a buck converter. Most of the Google searches I have done predict doom. I have a AC 240V / DC 24V 8.5A buck (fixed) that I wish to regulate with an adjustable buck of 10 A. I won't be using more than 5 A. I thought that a diode to stop any reverse spikes might be a good idea. Do you know of any reason why I can't ? Please help if you have the time.
I am wanting to do this but want it more sensitive, so how would you connect say 2 or 3 of them together to make it more sensitive and I will be using 12 volt power supply from an old computer.
but *why* does a negative bias make the depletion regions grow (and vice versa)? my intuition says me it should be the other way around, because by putting more electrons into a P-region you should make it attract stray electrons from the N-region *less*, because now it's more negative which means there's less reason for the flow of negative electrons (depleting from the N-region) into it. therefore the depletion regions should shrink intuitively. why don't they?
In Canada and USA, you can try ABRA Electronics (abra-electronics.com/index.php?subcats=Y&pcode_from_q=Y&pshort=Y&pfull=Y&pname=Y&pkeywords=Y&search_performed=Y&q=jfet+transistor&dispatch=products.search&page=1) among other places.
11:40 The PN body is globally neutral (no electrons are destroyed), at the junction, internally. While we can speak of isolation (the chanel becoming pinched), the voltage at the GATE get involve through the "free" electrons from the N type having moved to "pot holes", to "nests" (electronically) of the P type. That makes the P type with an excess of static electrons sitting in its "nests" and leaving the N-type with un-replaced electrons (depleted) since the bulk of the crystal, after all, it is not a good conductor, but a semi-conductor, when its free electrons are gone (in the nests of the P type). So, there is there, at the junction, a real *static* electric field built up, which blocks the curent flow better in a direction than in the other. If you reverse bias the junction, the depleted region of the N type increases, which make the chanel of the transistor less and less conductive... So while we can speak of isolation (mostly for the chanel of the transistor) it is more a static electric field ( 0.5V (surface mount, large slabs) to 0.7V ( discrete component) for silicium ) effect built around the P-N junction which is implied through the GATE voltage. Ref.:"Fundamentals of Microelectronics", second edition, Behzad Razavi, Wiley, pp36-next)
I have been told that they generate much less internal noise than most other transistors. They are somehow easier to use than CMOS (themselves easier than BJT), but have GREAT (really great) variability in their characteristics, even if they are the same part number and of the same batch!
Vgs ( V_at_the_gate minus V_at_the_source ) must be negative for a N-chanel JFET. Else, you may destroy it ( because then the PN diode conducts ( gate -> chanel) and damage the transistor ). So, under normal circumstances, no, you can't have a voltage at the drain, or at the source, lesser than what you have at the gate. In fact, static electricity can destroy the transistor too.
Hi sir please if you could answer. . I have a super capacitor bank with a protection board. . If i want the caps to charge And discharge at the same time .. what should I do?? It will mean alot if you answer
Personally, I would suggest to charge them in parallel, and discharge them in serial... with a minimum of resistance when you charge them since for 10F, the contant 5*R*C is about a minute for EACH single OHM of resistance ( 5 R C = 5 * 10 * 1 = 50 seconds ). I would use CMOS to change the configuration, "electronically", due to their possible very low resistance, NOT JFET though.
Julie, or anybody really, could you recommend a good “beginners” project that won’t break the bank. Beginners is in quotation marks as I have never really took on a major project, yet have knowledge of the arguing IDE, constructing breadboard circuits, and even stripboard circuits and etc. I ask only because I have no active income due to my age and you are my main source of knowledge, as I follow many of your videos to help me “get by” the scary world of hobbyist electronics.
Its all relative. You're making the 'positive' of that 1.5V supply relative to the 0V reference of the 9V battery - so that means the 'negative' of the 1.5V is now 1.5V *below* the 0V of the 9V supply - so that makes the -ve terminal of the 1.5V battery in essence -1.5V relative to the original 9V.
Connect the source through a resistor to negative of the battery, pick the value so there will be few volts dropped across that resistor at the current you want. That will lift the source above ground, so then by connecting the gate to ground you will reverse bias the p-n junction.
Julian himself explained it when he built a split voltage power supply using 3 galvanically isolated wall wart adapters. See "Julian builds: a split voltage power supply (+-12v and 5v) "
Since the montage is not connected to the home electrical distribution, its "ground" is "floating" so its "zero" is purely a convention. (Even if "grounded" to earth, you can go more negative than it, just like 0 degree Fahrenheit being more negative than 0 degree Celsius.) After all, a voltage is a difference on potential, and a while you report a single value for that difference, a difference implies two values, the second value, the "zero" or the "origine" is just being "assumed", or "conventional", but it is possible to use another "origine" and thus, get more "negative".
How about a lightning detector? that would ping and light a lamp with a lightning flash? I thought of a little "Haunted House" that would flash along with a real storm, just to let you know a storm was brewing.
The biggest problem I have with these devices is how much parameter spread you get, even with the same part number from the same batch by the same mfr...
Now, i have started my year off right. . Cheers , from Ralph Thomas, in Vancouver BC Canada, the BC, stands for the Province of British Columbia, other than what most know as Columbia, enjoy your videos, there is a calming effect to them.
What about using combining a LED acting as a light detector looking at the LED that is driven through a series pass transistor driven via an OP amp where the positive voltage sets the voltage to the driven LED and the voltage from the LED looking at the driven LED feeding back into the negative of the OP amp should allow the driven LED to operate like a LASER and not burn out.
If you are interested in tube/guitar amp sound/quality and have a 2N5457 JFET to play with, check out runoffgroove [dot] com's Fetzer Valve circuit/article (I have no affiliation with the site or it's content). I have built that circuit in front of all of my guitar amps as a first preamplifier input stage. It makes a real nice warm tube amp sound. If this preamp circuit is placed in front of an LM386 it makes a really nice sounding simple headphone amp. The circuit requires you to dial in the transistor's bias using a DMM or scope. This is probably the reason a circuit like this is not typically found on low end guitar amps. However, the person that is willing to take the time to dial it in, gets rewarded with an amp that sounds much much higher quality than most people expect from a typical solid state amp. -Jake BTW I tested all of the devices listed in the Fetzer article, and I think the 5457 sounds best. You absolutely must do all of the test measurements in the article too. Don't just use the averages given. My devices tested way outside of the averages stated in the article. I have not created any content on my channel about this or anything audio, so don't waste your time checking ;-)
Julien, About your last comment, 'they make very good current sources.' I like to make a constant current capacitor bleeder circuit using 2× N channel JFETs in a series circuit followed by a small LED. If this is placed across any large capacitor inside an adjustable power supply or project it lets me know if the capacitor is safe to handle without the need to check it with a meter. It's a really handy safety device. I usually just grab a couple of JFETs from little electret-can type microphones to make the circuit for free, as most electret mics have N-JFETs inside.
hi Julian i know maybe its not the right way to contact you can you plsssss help me i bought from t-happy (ps: i love your videos) a bluetooth 4ch relay and dont know how if you maybe make a video "5v 4 ch bluetooth relay android mobile remote control switch motor led light app"
But why during all this fiddling about does the LED not die? At the beginning, you say "...don't connect the LED directly across the battery because that would kill it". So why when biasing to get the LED brighter does the LED continue to work?? Thx.
Ok, I get that. Then the question becomes "will some gate bias ever turn the JFET on fully enough to kill the LED". I would have thought that a 10K resistor from gate to V+ would have turned on the JFET fully enough to kill the LED... but such was not the case.
That is interesting. I was kinda wondering that myself. I see what you were asking now. Ok, Julian, why didn't the led blow up when you made the JFET be fully closed? ;)
He stated in the video that the wire to silicone junction was ohmic, so there must be enough resistance to limit the current so that the LED does not blow even if the n-channel is fully conductive.
Good stuff mr. Ilett, thank you!
So many times you've provided the missing link between [basic] and [difficult] theory simply by spending time on understanding it and then explaining it with your own angle. Assembly language, MosFETs and now JFETs. Excellent stuff!
Of course it's your own prerogative to make whatever videos you'd like, but if you are unsure maybe a survey like Dave Jones did could be helpful? I'd vote for this kind of stuff. And finishing the Muppet.
Many thanks Julien. This is one of my favourite videos on UA-cam. I love it. Seriously. Great stuff.
Julian, you can never spend too much time learning new things!
HNY!!!
Julian, Happy New Year and thank you. This is fascinating!!!
Happy New Year Julian, all the best for 2018.
those are some pretty cool electric croutons you got there buddy
Happy New Year Julian, keep those videos coming :-)
Absolutely LOVE this! ❤ I've been using 2N3819s quite a lot lately but I was curious about symmetrical JFETs, also. I'd also like to ask, Julian, if the solder less breadboard is made by Lego? Gr8 upload, very enlightening easy for me to follow. Thanks. 🙂
Nice distraction on an otherwise boring day. Happy New Year Julian, from Las Cruces, New Mexico, U.S.A.
Happy New Year! Very interesting first video this year.
If you ever get back to playing with JFETS try the MPF102 she is highly sensitive, I have been building stand alone ghost detectors with these JFETS for some time now, they are very simple consisting of the JFET, an LED and if you wish to extend the antenna, solder on a 1 meg resistor. I didn't have one on had the other day, but needed to get one out the door for a ghost-buster outfit, so I soldered on a 1k ohm resistor, worked as well as the 1 meg, in fact I think it was a bit more sensitive. These little units can detect a fellow combing his hair two rooms away on a dry day, The way I build them is quit simple on a 9 volt plug with the skin removed, solder the Gate to the + terminal, the source through the LED to the - terminal, the Drain works as the antenna and is where to attach the resistor to extend the range. To use, simply hook it up to a fresh 9 volt battery and keep an eye on the LED, it will pick up any negative voltage flux within a room or two. I have three of them that I built using different methods, the second one is built on the same basis but using a plastic enclosure and having the works hidden as well as a toggle switch to add to the professional look. I have a few other type I have put to gather, one based on an Arduino to read the voltage and light up LEDs depending on strength, from one LED to 10 for full force. Another I built following Big CLive's video but instead of using rabbit ears, which I could not find in our small town, insted I mounted her on a project board, then used a couple of pieces of heavy copper wire recovered from an old Power Supply These things are great fun!
Excellent tutorial on j-fets. Thanks Julian.
lego combined with electronics is awesome .... nice little breadboard module things .... did santa give you a present julien? :P
U beat me to it "electric lego's"
They are called XF-25 mini breadboard
@Sick Vic, Just 'lego' mate. The plural is implied by the word itself ;)
Thanks Julian, for a nice introductory video. The reason why doping levels are so low is because a Silicon crystal with a small number of imperfections is required, rather than a Phosphorous or Boron (etc) crystal with Silicon imperfections. More than the minutest amount of imperfection is first of all overkill, and second far too disruptive of the Silicon lattice. Interestingly, it could take us days at temperatures between 950°C and 1275° C under extremely clean conditions to create those small doping levels. The diffusion process occurs very slowly, and a combination of dopant flow through the ovens, plus temperature and time control, allows for quite precise control of layer thicknesses, junction depths. (Wafer fabrication doesn't adhere to a normal working day!) This is one reason why CPU's, GPU's, and the like, are so expensive; there are a number of different dopant layers, and several intermediate cleaning and preparation procedures for each layer in the Silicon, each of which can take from hours to a number of days. One power outage can mean the loss of a number of batches of devices, each at different stages of manufacture. Chip yields, initial testing, selecting, packaging and re-testing also affect the factory prices.
Oh wow, I take it you're in that industry.
Nice. About those breadboards and the base plate, I've never seen such, what is the manufacturer and are there any more different modules to that system?
I remember a postbag where he got the mini breadboards, but the baseplate is a new one to me as well.
Okay. I know it's NOT Lego as some have said here, because the nubs are too high. EDIT: Or do you call them studs in Lego, anyways.
There is a company in the US called 5e and they make similar breadboards, but I do not know if they ship over seas.
Happy New Year Julian! Thanks for your videos. They teach us a lot. Could you please tell us where we can get one of these unique breadboard systems?
It's always awesome to see a video that just came out on a topic that I've been currently researching. By the way, where did you purchase those transistors from? Are there any good stores you would recommend depending on the country you're in? Thanks for posting this! And Happy New Year.
im just getting into electronics and im really enjoying it so far. i bought a strip of those MMBJ201 SMD and a pcb adapter board . im using them to act as the tubes in a marshal Plexi amp but in a pedal form and they sound really good. really good dynamics . if i pick my guitar softly its completely clean sounding no distortion, if i hit my strings a little bit harder it starts to break up with some distortion in a really nice sounding way. i very much enjoyed your video on these Jfets id like to learn more about all my transistors .
Thanks for sharing 😀👍 happy new year to you to
Ah, a drop of the good stuff. Technical investigations and explanations, the reason I subbed in the first place. Will this progress through into a practical application? You've got some other great projects on the go.
When you bring the gate positive w.r.t. source, it matters how much. If you bring it more than 0.6V (one diode fwd drop), you are actually injecting significant current through the gate. If you bring it e.g. at 0.3V, you are basically only enhancing the channel (as you do not yet have significant current through the diode).
So the question regarding your setup is are you enhancing the channel or also pushing current through that diode?
Happy new year. hope you had a great holiday . and New year!
Happy new year Julian. Will have to watch this again - too hung over to follow it properly :(
That looks really interesting. Now I'm a bit confused because there are op-amps with JFET inputs (like TL07x) to get higher input impedance, among other things. But from what you shown it seems like the leakage current is really high, compared to regular BJTs..
Happy New Year, Julian.
I've seen JFET circuits with "100 Meg" gate resistors made out of leaky reversed biased transistors... pretty sensitive stuff. See the inputs of the TL072 JFET op amp.
J112s make really good electric guitar buffer/signal boosters for use in the signal chain in front of other effects devices. 2N5457 is good too and J201 has much lower gain. Jerry Garcia's guitar had a 2N5457 based signal booster IIRC. You'll find lots of great JFET experimentation at DIY guitar effects sites like www.diystompboxes.com/smfforum/
Happy New Year!
@Julian reverse the polarity of the battery and of the LED in the circuit, then you can pull the gate fully down. Running the circuit in the opposite direction essentially switching between blocking and enhance modes?
On thhe subject of JFETs, you should do a video on lambda diodes. It's basically just a P type and N type jfet in series and has an operational region with negative resistance. Sort of like a tunnel diode, but higher voltage.
Interesting little devices these are. I work with vacuum tubes mostly but I greatly appreciate more modern solutions. Power consumption and size of devices made today would have been thought as impossible 50 years ago.
Hello, Julian... I'm big fun of your videos, howether I'm complete amateur... What you showed us here amazed me. i know, I'm noob. But, I have one very important question for you. I'm sure it's possible, but I have no idea how to make it on breadboar, so... If you don't mind? Is this possible to boost transistor reaction, so it could "feel" my finger from, let's say 5cms away or 10cms? I will play for sure with yourdemonstration, but my idea is to use the transistor to react on eletro-magnetic field (let's say 5cm) and then digitally use it as a bit (I guess another transistor could help me to turn 5V on when transistors is "in range"). Yeah, I will be reading and trying... My idea is to have two or three such transistors generating digital answers and the difference in time (small changes in time (measuread by simple timer) - should allow me to use these transistors for "simpliest radar"... Simply - if I know which transistor is closest to magnetic field - I know where is the source of the field... Well, maybe my sci-fi idea, I'm complete amateur, but I'm working on something, right know it's a software simulation, but I want to build it in breadboard first and then... I hope to build something very simple and very amazin - I must say. Have a good day!
So why is there a N and P channel fet...if you can exchange the Drain and Source??? very good video
A Happy New Year to you Julian :-)
Happy New Year Julian!
Thank you for a very clear and interesting explanation.
Julian, I'm just curious, is your job related to electronics or is it just your hobby?
So as I understand, this device is like an electron tube? Which one is closer to them? JFETs or MOSFETs?
That was a great JFET explanation!
You can build a complete E-field detector on the top of an upright 9v batt. (which is the power source) that will last for years, which will tell all sorts of things about the E-field (esp.in cold dry weather). On my bench, I have a large sheet of black conductive foam connected to earth ground. It has saved me many circuit components!!! often (VERY) when you sit at your workbench, and the LED glows bright--you need to touch the foam--sometimes the shock actually HURTS!! I have learned to make a fist and discharge the static through a tight-skinned knuckle. Or, better yet, tightly hold a small (somewhat long ~6") conducting rod and touch the other end to the foam--A VISIBLE DISCHARGE, BUT NO SHOCK AT ALL!!! Again, this can be spectacular in very cool dry weather.
--dalE
How to make +-12V supply from a single 1A 12v wallwart? In my Behringer Neutron the PSU is working from this little 12v wallwart. Is that some kind of inverting IC or it can be simpler?
Had a lot of fun with 2N3819's about 40 years ago...Leave the gate disconnected, then comb my hair nearby. (Also with a small lamp - LED'S too expensive then) and watch it flash, dim, go off as I moved to and fro the work desk.
The IGFET (Dual-gate) 40673 was a different kettle of fish! If one removed the ring shorting everything together before it was in-circuit, it was TOAST!
I remember a schematic for a CB receiver that featured a dual gate 40673. I think it was a book of projects for CB by Robert Penfold.
Used as a mixer, IIRC. I made a couple of Direct Conversion HAM Radio receivers with it. Useful li'll thing!
goo.gl/prCb5f
Those 40673's were so fragile! I fried a couple by desoldering them from a circuit, before reading the handling instructions. Later devices had internally-constructed protective diodes, which would allow for a little mishandling.
Happy New Year Julian. Some time ago you showed a fake LM2596HV going up in smoke. I noticed you powered it with a buck converter. Most of the Google searches I have done predict doom. I have a AC 240V / DC 24V 8.5A buck (fixed) that I wish to regulate with an adjustable buck of 10 A. I won't be using more than 5 A. I thought that a diode to stop any reverse spikes might be a good idea. Do you know of any reason why I can't ? Please help if you have the time.
What I really want to know is, what is thatlego breadboard setup you’re using?
Happy New Year Julian
or could you make it sensitive enough and record data at high speed from each one, would you see slow motion of wifi signals or etc?
where did you find the lego bread board pcs ???? they are cool
Maybe you could make a theremin with it
I am wanting to do this but want it more sensitive, so how would you connect say 2 or 3 of them together to make it more sensitive and I will be using 12 volt power supply from an old computer.
I love connecting the gate to the sauce!
Happy New Year to Julian and all subscribers! And... Julian, DON'T BE SO NEGATIVE! ;-)
+der Birnodin he he :)
squelch olarak kullanılır mı?
If you make a cube array of these, that's 10x10x10 and space them 6 inches apart could you get an x-ray of a ghost?
please make more videos on FET if possible.
And all other transistors. They are the key to really understanding electronics.
but *why* does a negative bias make the depletion regions grow (and vice versa)? my intuition says me it should be the other way around, because by putting more electrons into a P-region you should make it attract stray electrons from the N-region *less*, because now it's more negative which means there's less reason for the flow of negative electrons (depleting from the N-region) into it. therefore the depletion regions should shrink intuitively. why don't they?
Nice video! Where did you buy your JFETs?
In Canada and USA, you can try ABRA Electronics (abra-electronics.com/index.php?subcats=Y&pcode_from_q=Y&pshort=Y&pfull=Y&pname=Y&pkeywords=Y&search_performed=Y&q=jfet+transistor&dispatch=products.search&page=1) among other places.
Transistors on dope, no wonder windows can be a sloth.
Actually, Good video. I feel like I learnt something.
11:40 The PN body is globally neutral (no electrons are destroyed), at the junction, internally. While we can speak of isolation (the chanel becoming pinched), the voltage at the GATE get involve through the "free" electrons from the N type having moved to "pot holes", to "nests" (electronically) of the P type. That makes the P type with an excess of static electrons sitting in its "nests" and leaving the N-type with un-replaced electrons (depleted) since the bulk of the crystal, after all, it is not a good conductor, but a semi-conductor, when its free electrons are gone (in the nests of the P type). So, there is there, at the junction, a real *static* electric field built up, which blocks the curent flow better in a direction than in the other. If you reverse bias the junction, the depleted region of the N type increases, which make the chanel of the transistor less and less conductive... So while we can speak of isolation (mostly for the chanel of the transistor) it is more a static electric field ( 0.5V (surface mount, large slabs) to 0.7V ( discrete component) for silicium ) effect built around the P-N junction which is implied through the GATE voltage. Ref.:"Fundamentals of Microelectronics", second edition, Behzad Razavi, Wiley, pp36-next)
What are they used for? Can you control the resistance in a circuit with one?
I have been told that they generate much less internal noise than most other transistors. They are somehow easier to use than CMOS (themselves easier than BJT), but have GREAT (really great) variability in their characteristics, even if they are the same part number and of the same batch!
Since D and S are basically the same (symmetrical) can JFETs be used to switch AC voltage?
You want a TRIAC for that
Vgs ( V_at_the_gate minus V_at_the_source ) must be negative for a N-chanel JFET. Else, you may destroy it ( because then the PN diode conducts ( gate -> chanel) and damage the transistor ). So, under normal circumstances, no, you can't have a voltage at the drain, or at the source, lesser than what you have at the gate. In fact, static electricity can destroy the transistor too.
I read that JFETs can act as voltage controlled resistors, just as what happened at 16:32.
Hi sir please if you could answer. .
I have a super capacitor bank with a protection board. . If i want the caps to charge And discharge at the same time
.. what should I do??
It will mean alot if you answer
Personally, I would suggest to charge them in parallel, and discharge them in serial... with a minimum of resistance when you charge them since for 10F, the contant 5*R*C is about a minute for EACH single OHM of resistance ( 5 R C = 5 * 10 * 1 = 50 seconds ). I would use CMOS to change the configuration, "electronically", due to their possible very low resistance, NOT JFET though.
When I turned my jfet around (j111) it will stay on all the time...put it back the way it should be and it acts like yours with an off and on..
I want to know are they compare to mosfets as linear amplifiers
rflberg They have a very high input impedance, but they aren't completely linear.
Julie, or anybody really, could you recommend a good “beginners” project that won’t break the bank. Beginners is in quotation marks as I have never really took on a major project, yet have knowledge of the arguing IDE, constructing breadboard circuits, and even stripboard circuits and etc. I ask only because I have no active income due to my age and you are my main source of knowledge, as I follow many of your videos to help me “get by” the scary world of hobbyist electronics.
Happy new year !!
But no led resistor?
Happy 2018 Julian :)
Adding the second battery is a little confusing. Anyone able to explain how you can make something "more" negative?
Its all relative. You're making the 'positive' of that 1.5V supply relative to the 0V reference of the 9V battery - so that means the 'negative' of the 1.5V is now 1.5V *below* the 0V of the 9V supply - so that makes the -ve terminal of the 1.5V battery in essence -1.5V relative to the original 9V.
Connect the source through a resistor to negative of the battery, pick the value so there will be few volts dropped across that resistor at the current you want. That will lift the source above ground, so then by connecting the gate to ground you will reverse bias the p-n junction.
Julian explains this at 13:57 Depends on the polarity of two voltage sources (batteries).
Julian himself explained it when he built a split voltage power supply using 3 galvanically isolated wall wart adapters. See "Julian builds: a split voltage power supply (+-12v and 5v) "
Since the montage is not connected to the home electrical distribution, its "ground" is "floating" so its "zero" is purely a convention. (Even if "grounded" to earth, you can go more negative than it, just like 0 degree Fahrenheit being more negative than 0 degree Celsius.) After all, a voltage is a difference on potential, and a while you report a single value for that difference, a difference implies two values, the second value, the "zero" or the "origine" is just being "assumed", or "conventional", but it is possible to use another "origine" and thus, get more "negative".
Interesting but what practical use in a circuit
Where do I get those tiny breadboards! I want:-)
you can get them on ebay, 7 for a pound. search for "25 point breadboard"
Happy New Year, even though it's just an arbitrary unit of time we humans invented!
How about a lightning detector? that would ping and light a lamp with a lightning flash? I thought of a little "Haunted House" that would flash along with a real storm, just to let you know a storm was brewing.
happy New year
Semiconductors are just so weird... Imagine the R&D that goes into modern CPUs... 100 million transistors per square millimeter...
Happy new year Julian! I was looking forward for your next video.
Lovely!
Anyone done reversed source drain transfer curves? Also enhancement curves?
The biggest problem I have with these devices is how much parameter spread you get, even with the same part number from the same batch by the same mfr...
Thank you.
0:45 lol no thats either magic or cheating. everyone knows you cant turn transistors on and off just by pointing at them
Field effect transistors ARE magical.
If you really snarl at some of them, they can die of fright!
oh yes you can...a mosfet can do this too...
what sorcery is this :/
Not sorcery! Wizardry!!!!
Black magic
That escalated quickly ...
Now, i have started my year off right. . Cheers , from Ralph Thomas, in Vancouver BC Canada, the BC, stands for the Province of British Columbia, other than what most know as Columbia, enjoy your videos, there is a calming effect to them.
Happy 2018
Can you make a smaller drawing on a big sheet of paper?
Edit: I jumped the gun, you covered what I said hehe
That was a very interesting video, Happy New Year!
What about using combining a LED acting as a light detector looking at the LED that is driven through a series pass transistor driven via an OP amp where the positive voltage sets the voltage to the driven LED and the voltage from the LED looking at the driven LED feeding back into the negative of the OP amp should allow the driven LED to operate like a LASER and not burn out.
Wishing the best of 2018 to you
If you are interested in tube/guitar amp sound/quality and have a 2N5457 JFET to play with, check out runoffgroove [dot] com's Fetzer Valve circuit/article (I have no affiliation with the site or it's content).
I have built that circuit in front of all of my guitar amps as a first preamplifier input stage. It makes a real nice warm tube amp sound. If this preamp circuit is placed in front of an LM386 it makes a really nice sounding simple headphone amp.
The circuit requires you to dial in the transistor's bias using a DMM or scope. This is probably the reason a circuit like this is not typically found on low end guitar amps. However, the person that is willing to take the time to dial it in, gets rewarded with an amp that sounds much much higher quality than most people expect from a typical solid state amp.
-Jake
BTW I tested all of the devices listed in the Fetzer article, and I think the 5457 sounds best. You absolutely must do all of the test measurements in the article too. Don't just use the averages given. My devices tested way outside of the averages stated in the article. I have not created any content on my channel about this or anything audio, so don't waste your time checking ;-)
Reference:
www.runoffgroove.com/fetzervalve.html
Julien,
About your last comment, 'they make very good current sources.' I like to make a constant current capacitor bleeder circuit using 2× N channel JFETs in a series circuit followed by a small LED. If this is placed across any large capacitor inside an adjustable power supply or project it lets me know if the capacitor is safe to handle without the need to check it with a meter. It's a really handy safety device. I usually just grab a couple of JFETs from little electret-can type microphones to make the circuit for free, as most electret mics have N-JFETs inside.
Could you use the field effect as a digital end stop?
Happy New Year!
Happy new year :)
HNY Julian :)
Happy NEW YEAR !!!
hi Julian
i know maybe its not the right way to contact you
can you plsssss help me
i bought from t-happy (ps: i love your videos) a bluetooth 4ch relay and dont know how
if you maybe make a video
"5v 4 ch bluetooth relay android mobile remote control switch motor led light app"
Indeed they make current sources. Check out Karl Adams channel for a video on jfet current sources.
But why during all this fiddling about does the LED not die? At the beginning, you say "...don't connect the LED directly across the battery because that would kill it". So why when biasing to get the LED brighter does the LED continue to work?? Thx.
He says that the JFET "limits" the current. That's why no resistor is needed. The current is never fully 100% allowed to flow.
Ok, I get that. Then the question becomes "will some gate bias ever turn the JFET on fully enough to kill the LED". I would have thought that a 10K resistor from gate to V+ would have turned on the JFET fully enough to kill the LED... but such was not the case.
That is interesting. I was kinda wondering that myself. I see what you were asking now. Ok, Julian, why didn't the led blow up when you made the JFET be fully closed? ;)
He stated in the video that the wire to silicone junction was ohmic, so there must be enough resistance to limit the current so that the LED does not blow even if the n-channel is fully conductive.
+Korishan because the n channel always has some resistance, maybe 20 ohms or such like.
.
Nice Video 👍 , but you should really work on your shooting angles. and probably buy a flexible tripod.
+Pedram NOMAN in what way?
for example when your are drawing camera angle should be >80° , wide shot and 45° are not convenient
BTW, very informative video !
Happy New Year Julian
Happy New Year Julian!
Happy New Year Julian