2n2222a negative differential resistance

Рет қаралды 7,164

3 жыл бұрын

2n2222a negative differential resistance
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Пікірлер: 57

@dancollins1012 3 жыл бұрын

Did I miss it, or was there no schematic? A schematic should be shown even for simple circuits

@KissAnalog 3 жыл бұрын

Great video Paul!!!

@harshitaharshita6543 3 жыл бұрын

Love from India 🇮🇳

@stevetobias4890 3 жыл бұрын

Very cool effect Paul. Would have liked to see you run the circuit without the transistor and then put it in to see the real effect differential. Only because the capacitor and the LED are both connected to the resistor and ground line. It's interesting that the base is floating and this is why I wanted to see both sides. Guess I will have to try it myself.

@acmefixer1 3 жыл бұрын

This circuit uses the Vebo emitter to base reverse breakdown voltage, which is given as around 5 volts for silicon transistors. "But the base isn't connected!" you say. When the collector is connected to negative, the base to collector junction is forward biased and acts like a diode connecting the collector to base! This 5V Vebo is supposed to *never* be exceeded because a few volts above 5 V, the emitter to base junction goes into avalanche breakdown. This avalanche breakdown can cause permanent damage to the junction. But the avalanche breakdown causes the circuit to act like a neon lamp relaxation oscillator. Since this Vebo breakdown voltage could be any voltage above about 5 volts, the circuit has no guarantee that it will work. If the breakdown voltage is above the supply voltage, it will never break down and never oscillate. The avalanche breakdown caused the transistors I've used to permanently lose current gain or hFE. The hFE may measure 250 before avalanche, and under 200 after. BTW, 2N2222A transistors originally came in the metal TO-18 package. All plastic equivalents should not be marked 2N2222A, the usual is MPS2222A, PN2222A, etc. The plastic package does not directly substitute for the 2N2222A because it can't handle a full watt of power. Thanks for the video.

@CAsCurryKitchen 3 жыл бұрын

"This circuit uses the Vebo emitter to base reverse breakdown voltage, which is given as around 5 volts for silicon transistors." No, this is an NPN transistor the BE junction is forward biased so that's not correct. EDIT, ignore this I was reading the pinout of the transistor wrong.

@keithking1985 3 жыл бұрын

it would have helped new comers if you had a schematic with this little lesson. really cool video Paul. you need to check out the 2n2222a data sheet. it looks likes the cap charging, but also the breakdown of the transistor plus the diode. maybe all three!(of course all three) you could be getting oscillation going to. look in closer on the scope at different voltages and see if your getting a clear ringing or more of a charge up & down/diode breakdown. very interesting find..try it with a normal diode too.(coz LED's are bad at blocking) bet the results a very different. HUGE THUMBS UP.

@englishrupe01 3 жыл бұрын

Very cool and interesting video......thanks Paul!

@jensschroder8214 3 жыл бұрын

You can swap an NPN transistor E and C and it still works. But above a certain voltage, the current breaks through from E to B. This makes the route E to C conductive. The route C to B can withstand higher volts.

@williefleete 3 жыл бұрын

What is happening is likely due to the reverse breakdown voltage of the BE junction being exceeded and self triggering the base causing the transistor to turn on and discharge the cap through the LED until the cap voltage drops below the breakdown voltage. Explains the voltage dependency a bit. It seems a bit like a solid state relaxation oscillator.

@alessioulivi6734 3 жыл бұрын

I can't think of anything else but this, also because current is actually flowing, so it must have happened

@TheTubejunky 3 жыл бұрын

I found this data sheet www.onsemi.com/pdf/datasheet/p2n2222a-d.pdf I'm sure there is something in there about 10v causing this affect.

@dalenassar9152 Ай бұрын

A schematic at the start would make ALL the difference!!!!!! INTERESTING VIDEO!

@PhG1961 3 жыл бұрын

Apparently someone had to make a remark about your hands, being a little too large... Unbelievable ! What kind of people are making this kind of stupid remarks. I thought this channel was all about te content. Not your looks... Anyway, just ignore them. I hope you can hang on many more years and continue with your work. I and so many others enjoy and appreciate your effort and work !

@peterjantzer4767 3 жыл бұрын

The correct term is 'Bassackwards'.

@marcdraco2189 3 жыл бұрын

Centrifugal doesn't exist, centripetal is the one that does. It's rather like conventional current flow and electron flow. Catches me out ever damn time too.

@frankowalker4662 3 жыл бұрын

Cool. Nice simple way to get a flashing LED.

@acmefixer1 3 жыл бұрын

The schematic for this avalanche mode oscillator can be found here. www.codrey.com/electronic-circuits/avalanche-pulse-generator-an-introduction/

@turbulent-582 3 жыл бұрын

Question? if you increase or decrease the environment temperature, does the frequency change?, if the capacitor value change does frequency change? a possible xtal substitute???? lol.

@zyghom 3 жыл бұрын

this board is full of capacitance - did you try using "spider web" connections? switching power supply is high frequency device - did you try with battery (Really constant DC voltage)?

@trelligan42 3 жыл бұрын

Good ideas both. I'd think the capacitance is low enough at ~20khz to not matter, and the power supply output is internally filtered - but you don't know until you test it. I can imagine a scenario where a high-frequency component from the power supply tickles the base just enough to lower the avalanche voltage from nominal.

@dmeemd7787 3 жыл бұрын

What's a great transistor refuse to learn with and use in general. You need some really great stuff them. :-) Centrifical is the outward force :) It took me a minute to figure out the circuit the first time I ever built one. I didn't want to look up why it was doing it I wanted to try to get a hypothesis and then test it what I did look up exactly how it works :-)

@Andrewatnanz 3 жыл бұрын

what form of sorcery is this ????

@abdulbasyirmohddahalan3374 3 жыл бұрын

Im a guitar player where one day my homemade volume pedal was broken.but something weared that the transistor is still working.then realized that i have put it backward or in invented order.start from that day i develope my automatik network switches using this " unknown phenomenon". 4 years later i heard that this could be named as " negatif resistance effect". Now i have 15 years with this effect and will come out with my video soon.

@keithking1985 3 жыл бұрын

i'd love to see that video!!

@abdulbasyirmohddahalan3374 3 жыл бұрын

@@keithking1985 alright just wait.its 3 switches in a network which once i touch the plate it will cancel the previously touched another switch.we can call this as " random automatik network switches". Maybe it will be the simplest random switches using negatif resistance effect.just maybe ha ha.

@ozzymandius666 3 жыл бұрын

If I remember correctly, negative resistance is an integral part of the fascinating Chua circuit.

@melplishka5978 3 жыл бұрын

That’s weird, usually takes around 12 volts to overcome the internal resistance of the bjt.

@bblod4896 3 жыл бұрын

Actually, you do have a curve tracer. I believe the transistor checker you got has the ability to output curves to a computer. Check it out. Thanks for the video, I'll try that at home.

@learnelectronics 3 жыл бұрын

You're right!

@trelligan42 3 жыл бұрын

Centripetal Acceleration is the 'real' force that makes centrifuges work. But if you take that same inertial equation and solve it for the rotating point of view, you get centrifugal force exactly. They are the same thing from different points of view. Only physics snobs insist on only using the term Centrifugal Acceleration.

@michaelpadovani9566 3 жыл бұрын

New concept to me

@DIYwithBatteries 3 жыл бұрын

It's a very old circuit Sir! although I watched it like a unique one lol

@electronic7979 3 жыл бұрын

👍

@fertilizerspike 3 жыл бұрын

You didn't explain the differential aspect. Differential between what and what? The term "negative differential" suggests a relationship between two resistances that is normally positive but gets inverted which means one or both resistances change. Which two resistances invert in this circuit? I assume the resistance of the resister doesn't change. Is it two resistive loads in the transistor or what?

@acmefixer1 3 жыл бұрын

Negative differential resistance is trying to say that between the two positive voltage points consecutively applied to a device, the current decreases instead of increasing like a normal resistance.

@fertilizerspike 3 жыл бұрын

If i had to try to figure out why this circuit behaves like that I'd suppose that when the breakdown voltage of the transistor was reached the full voltage drop of the diode applies which lowers the voltage across the transistor. I don't see what some imaginary complicating force has to do with it. The resistor would divide the voltage of the capacitor so changing that would also change the capacitor time constant? I don't know how it all works but just saying "it's all because of an imaginary force i looked up on Google after i discovered super fast transistors exist!" is not an explanation. Maybe in the navy they get away with explaining it like LEGOs to technicians but they do that to keep the bullet catchers from getting too smart.

@hugocoolens 3 жыл бұрын

This is an avalanche transistor circuit see e.g. Electronics World, september 1967, p.30...32. The "centrifugal/centripetal/pseudoforce" explanation is plain nonsense. Just show your viewers the IC=f(VCE) characteristic and point out the region with negative incremental resistance, with that knowledge you can explain the operation of the circuit correctly.

@MrMattberry1 3 жыл бұрын

I would have liked to understand more of what was actually happening

@trelligan42 3 жыл бұрын

Yeah, this video needs a deep-dive with a schematic and transistor graphs.

@kalikatz2382 3 жыл бұрын

Cool

@melplishka5978 3 жыл бұрын

Avalanche time lol

@hinkelstein4six 3 жыл бұрын

The base-emitter-diode is operating in reverse and acts like z-diode. The base is roughly at the same potential like the collector. The reverse base-emitter-diode has a breakdownvoltage of roughly 6 to 10 volts depending of the transistor type. When the capacitor is charged to a high enough voltage the base-emitter-diode has it breakdown and a avalangeeffect happens. Because of the circumstance, that the transistor is a current amplifier, the emitter-collector-path switches on and the capacitor gets discharged. That's more the function of a DIAC or trigger diode. It has nothing to do with the tunnel effect and the way that tunnel diodes work.

@CAsCurryKitchen 3 жыл бұрын

"The base-emitter-diode is operating in reverse and acts like z-diode. " No that's not right, it's an NPN transistor so here the BE junction is forward biased. And the CB junction, which is reversed biased and so could break down, still can't because its breakdown voltage is 40V minimum and he's driving it from about 9V supply.

@hinkelstein4six 3 жыл бұрын

@@CAsCurryKitchen you're a little bit wrong. First we have to realize that the transistor is forced to operate in a reversed manner. The collector is attached to a lower potential than the emitter. That means that the collector-base-diode is forward biased and the emitter base-diode is reversed biased. Therefore the behavior of the transistor is a little bit weird. I think you should do a little experiment. Grab yourself a breadboard, a npn-transitor, a 1kΩ-resistor, an adjustable power supply, a voltmeter, and some peace of wire to make some conections. Attache one leg of the resistor to the positive rail of the power supply and the other leg to the emitter of the transistor. Connect the base of the transistor to the negative rail of power supply. Than connect the voltmeter across the emitter-base-diode. When you now supply different voltages to that circuit, you will realize that below a certain value the voltmeter readings are roughly the same as the the applied voltage. Above that certain value the voltmeter readings will stay at the same value when increase the applied voltage. That's the behavior of a Z-diode. If you have also a LED and capacitor, you can than build the circuit, that is shown in this video. If you also have a oscilloscope you could measure the voltage between the base and collector and the voltage between the the collector and the emitter, possibly at the same time. And I'm pretty sure that I am right.

@CAsCurryKitchen 3 жыл бұрын

@@hinkelstein4six "The collector is attached to a lower potential than the emitter. " How do you figure that when the collector is connected to the positive rail through the resistor and the emitter is connected directly to ground? Look at the 2N2222 pinout. EDIT, It's ok I was reading the pinout wrong so i agree with you.

@hinkelstein4six 3 жыл бұрын

@@CAsCurryKitchen the emitter is attached to the connection between the resistor and the capacitor and the collector is attached to the LED. That is explained in the video. Watch with care and listen to the things that said really early in the video.