Classic Circuits You Should Know: Constant Current Source

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Classic Circuits You Should Know: Constant Current Source
You can use a single NPN BJT to make a simple constant current source. The output of the BJT is a function of the input current to the base times the BETA (amplification). yes there are more stable and better ways to do this but this circuit if the foundation. You can set the output current by dividing the voltage at the base - .6 by the emitter resistance.
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Me: Paul, 49 from USA
Education: United States Navy, University of California at San Diego B.S. E.E., University of Pittsburgh M.S. E.E.
Experience: United States Navy STS, Bayer Intnl Process Engineer, C.C.A.C AP of EE
Current: Retired
Health: BAD (Congestive Heart Failure)
Hobbies: Electronics, flying, amateur radio, music (classic rock)

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2 окт 2024

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Комментарии : 271

@arthurgiannakis2156 5 лет назад

I admire your willingness to teach but need to point out that a true constant current circuit will deliver the same current not just into a varying load but also from variances in Vcc. What you have is a current sink. If you vary Vcc even fractionally, the collector current (the load current) will shift accordingly. It's no longer constant. If you further expand your equation for Vb it approximates Vb = Vcc*(R2/(R2+R1)). This you can then substitute for Vb in your equation. If Vcc changes then Vb changes and so IL changes. Your circuit requires Vcc to be rock solid regulated for constant current to be realised. Not viable for loads that run directly off a battery for instance where terminal voltage falls over time as load is applied.

@petarmiletic997 4 года назад

Replace R2 with 2 diodes in series and you get constant current, Ic=Vdiode/Re

@boblewis5558 4 года назад

Not completely true, as using two diodes in the bias chain solves the vcc problem for any reasonable deviations. See my comment above.

@treelibrarian7618 4 года назад

I knew we had a problem as soon as he said Re was to "reduce thermal runaway" ... my favourite CC is similar but 2 transistors - replace R2 with a second npn (T2) with its base to the emitter of T1, emitter to ground, and collector to the base of T1. Vre is now 0.61V whatever else goes on, as long as enough current is coming down R1 to power the original transistor. Thermal changes in T1 are irrelevant. Can sink constant current down to less than 1V from ground (which is often important). Since transistors, resistors and diodes all cost the same these days (1p), there's no cost penalty and R1 value is now arbitrary, so when there's a charge for each extra value in the pick-and-place machine you can substitute a value already used elsewhere... win win win. Turn the whole thing upside down with pnp's for a CC source instead of sink. Re sets the current, rather than having anything to do with thermal runaway.

@boblewis5558 4 года назад

@@treelibrarian7618 yup! Same principle as signal diodes, but even better overall and as you say bugger all difference in cost and same component count.

@treelibrarian7618 4 года назад

@Kevin Counihan , I just can't imagine what that extra resistor would protect against. If T1 is already short, worse things are already happening - does it matter what happens to another 1¢ component? otherwise, sounds like wise practice to use it for testbench supply, though one CC would be enough? fun fact: T1 can also be a MOSFET and then higher currents can be controlled easily.

@DavidWatts 5 лет назад

I thought I had left my multimeter on.

@learnelectronics 5 лет назад

Lol it was mine

@gartmorn 5 лет назад

My poor dog is so jumpy and she noticed your meter was on Paul!

@mikehermesmeglio 5 лет назад

I thought it sounded like the sleep function on a Hakko soldering iron

@chloejackson-reynolds418 5 лет назад

@@mikehermesmeglio They go to sleep?

@mikehermesmeglio 5 лет назад

@@chloejackson-reynolds418 Yes. They have a sleep function to reduce tip temperature and then eventually it will shut off completely if it's not being used.

@thebeststooge 5 лет назад

You are moving up in the world as you were just in my recommended videos.

@learnelectronics 5 лет назад

Awesome, I didn't know RU-vid even knew who I was.

@sliderulelover 3 года назад

Great video. If you wanted to make this circuit a variable current source, all you need to do is replace R1 and R2 with a potentiometer with the wiper blade going to the base of the transistor. To vary the current, just turn the knob of the potentiometer increasing or decreasing the current to whatever value you want. I would start with a 100K potentiometer first and see how it behaves. Other potentiometers are also possible.

@johncundiss9098 5 лет назад

A constant current source requires a way to MEASURE the current flowing through it.

@immortalsofar5314 4 года назад

Question from a dangerous tinkerer here. So... if I scaled this up with a 600A power transistor, could I use this technique to get a constant 200A for welding?

@edism 5 лет назад

That's not a constant current *source*.

@duanecjohnson 4 года назад

Hi Ed; The classic circuit uses 2 transistors, one connected as a diode to compensate for the B-E drop of the second. See: Current Mirror en.wikipedia.org/wiki/Current_mirror en.wikipedia.org/wiki/Widlar_current_source redrok@redrok.com

@boblewis5558 4 года назад

I think you're being a little pedantic now. You could say sink, but it could also be said the the power supply is the constant current source. I must admit, most of the time I have used a CC source, it's been using the PNP variation. But it's just the inverse of the exact same circuit reliant on the constant voltage being created across the emitter resistor. Swings and roundabouts really. Most engineers would accept both circuits as current source, especially with diodes in the base bias chain

@henrikjensen3278 5 лет назад

Let my start by saying Happy Birthday But I will not give your a passing grade for that constant current source. Replace R2 with a red LED or two diodes would help because it will reduce its dependency on input voltage, but a even better solution is a JFET, it is a constant current source sometimes without external components, sometimes you need a single resistor. None of the above is perfect, you need something with a stable reference and more gain to be closer to perfect. In one of my designs I needed a a led (Opto coupler) to work from as low possible voltage to as high as possible voltage, a JFET did that nicely, my final design is rated from 4V to 25V and includes a polarity protection diode, a opto coupler, a red LED and a JFET with resistor to limit current. Low limit is due to voltage drops in the different part, high limit is due to the JFET.

@tonypitsacota2513 10 месяцев назад

Is your Vcc 12.0 volts? My amperage was very low using a 5.0 volt in LTspice simulation. 508uamps

@rolandberendonck3900 5 лет назад

Very usefull and helpfull video, thanks :). And Happy Birthday Paul with your 50th!!! anniversary!!!!!!!!!

@Ian.Valerio 3 года назад

Happy belated birthday! I hope you enjoyed your cup of cake :)

@Inquire98 5 лет назад

"Thank You", thank you very much for the diagram and formulas. That was REALLY great 😋😎😋

@amitkhulbe 3 года назад

Will current be constant on changing the load?

@kwtmmm614 5 лет назад

First of all WISH YOU HAPPY BIRTHDAY TO YOU SIR. classically explained. 🎂🎂 🌹🌹🎂🎂.

@billfield8300 5 лет назад

Now this is the content I'm looking for. Happy Birthday and keep up the good work.

@interestingspagetti 5 лет назад

You totally lost me! But your vid's are awesome. I'm currently (excuse the pun) trying to order 3 mosfets to power a cheap rgb 5 metre reel so to pwd from an arduino which i don't know how to do yet. Do i get a tip120 or a lrlb8721 or many others that will suffice? Digikey confused me. I'm 49 years old, but never too old to learn. I'm dedicated to building arduino things this year and learning to get the basic's of coding. Yes there are lots of examples out there. But i Wanna understand it all also. I'm sure it will get easier as i order different chips, mosfets, capacitors etc and building them on to boards. I have a basic knowledge of electronic's and some really good idea's for arduino's. Watch this space. But thank you for helping me on my journey, along with many other sources. Adding another transistor would make it a darlington transistor (tip120)? Ps: Happy Birthday and New Year :)

@GiganT09011994 5 лет назад

I used IRLB8721's and it works pretty great. They dont heat up at all, altho its only for about 40cm. I think for 5m youd need a heatsink

@pepe6666 5 лет назад

good on ya. arduino is an excellent place to start. learn how to control stepper motors and you're like basically able to make robotic things. its such an enabler. you can make anything. also check out 18650 batteries on aliexpress and the wee bat charger chips for them

@chanc.7648 Год назад

Great clip, many thks.

@meax7180 6 месяцев назад

can I use this circuit as cc li ion battery charger?

@djberg3483 5 лет назад

Good stuff, thanks. And as many who commented before me have said, happy birthday sir! Also, by the bits of all this I am grasping, if you were to put a potentiometer in r2, that would give you the same scenario as the current adjustment potentiometer on a benchtop power supply? Thanks for the stimulation of mental growth in me and my kids as well.

@ashave9100 5 лет назад

Hi There I have just found your channel and it looks Ok ! Would it be possible to finish the sums off please-you are a good teacher but , why did you stop ? Thank you- by the way-happy birthday !!

@KiwiPowerNZ Год назад

My problem is Re and the power dissipated gets high if you want a 10A 12V constant current source. Is there a better way when you’re getting into higher currents? The application for the circuit is to charge a super capacitor bank without melting wires or blowing fuses.

@adamedwards2435 5 лет назад

Great tutorial on constructing a constant current source. Theory then hands on labs are the only way to learn electronics. Thanks Paul and happy birthday.

@Enjoymentboy 5 дней назад

This was exactly what I needed. I have had a bag of at least 1000 2n2222s for about 35 years and this will put them to good use... finally

@cezarcatalin1406 4 года назад

You can make a constant current source with a diode in reverse on the base of a transistor. The reverse leakage current through the diode will not change much with voltage, the transistor will amplify the constant reverse current from the diode. OR JUST USE A SINGLE JFET WITH THE BASE AND THE DRAIN TIED TOGETHER GODDAMNIT !

@Brainwizard.2 4 года назад

The equation in the End is not right. Damn.. He took the circle with U2, Ubase_emitter and Uemitter. ->UB, 0.6 and IE * RE Which means: IE = (UB-0.6) / RE Because 0.6Volts at the transistor means conducting: IE = alpha* IC so the result is: IC =[ (UB-0.6) / RE] * alpha. Damn. Please correct that. I calculated for 30 minutes, because i was unsure of the result. Teaching is fine, aslong as it is complete and fine. Also continue step by step. Gosh and dang.... !

@johncundiss9098 5 лет назад

Do you own a constant current power supply? I must assume you do not. Hook your led to a constant current power supply and set it for 10 milli amps. Now turn it on, led lights. turn up the voltage to anything you want, the led will remain the same. in fact you can add more led in series and they to will, remain the same. THUS IF YOU CANNOT SHOW IT YOU DO NOT KNOW IT. SHOW ME! ! ! SHOW ME! ! ! SHOW ME ! ! ! I AM WATCHING.

@deadpenguinss 4 года назад

Confused by the last equation. You wrote ILoad = (Vb - 0.6 / Re) But I don't see how that can be true, because that's what Ibase equals (if you solve for it). Your previous lines of equations can be re arrangement to make the statement that Ie = Ib + Ic Since Iload = Ic Isn't it simply Iload = Ie - Ib? Since you said Ie = 437Ib Then, Iload = 437Ib - Ib = 436 Ib The only way Iload can be dependent on Re as per your equation is if Ib is dependent on it. To me it seems you are missing a factor of 436 in front of that last equation

@johncundiss9098 5 лет назад

I like hopw you Highlight a reply especially since YOU ARE WRONG. Change the voltage and the current through that led will change. UI think you need to stop and read the LM317 datasheet. Just that itself will teach you what constant current is. All you have is a current control through a transistor. If you change voltages the current will change. Now take you a lm317 and connect it up as they show you for constant current. You will e able to crank in that thing anywhere from 5 volts up to its general rating of 37 volts and that led will not falter. YOU ARE WRONG.

@vivekvenkatsubramaniam437 5 лет назад

Happy birthday! Have a good one! Really useful video! I have a doubt, though, could I use this sort of circuit to test a lithium ion/lipo battery discharging? Or would that be overkill for this?

@dvaVivy 4 года назад

Hello can anyone help me? I was trying to make a double A battery charger 1.2V NI-MH I have successfully created the proper voltage rating for the battery, but I was having trouble with getting a constant reasonable enough current to charge it. I'm only having at best 10mA on the output load.

@benjaminbrower540 11 месяцев назад

Have you ever built a power supply for your bench top? Could you do it with used electric parts from old tvs, and things like that? Or a inverter...and converter build?

@moejoe987654321 5 лет назад

If the "Load" is a capacitor, can I connect the other end to a separate circuit instead of back to Vcc? (so I can get a linear change in V vs t based on the charging of the capacitor with a constant I source)

@moejoe987654321 5 лет назад

No, that is not how that works.

@beakytwitch7905 Месяц назад

Use a voltage regulator such as 7805 driving a steady load. The load gets a constant voltage across it, so it draws a constant current. Then the voltage supplying the regulator puts a constant current through the regulator. In fact it is not a constant current source, more accurately is a constant current sink...

@hichamtassi1753 3 года назад

Hello, nice video ! How to do to have a constant current but not 3mA, i would need 1Amp for battery charging. The same circuit can do the job ? Thanks

@WistrelChianti 2 года назад

Honestly... I feel I learnt nothing other than how to cheat an exam. Useless. I've come away with zero understanding of why or how this is working.

@dvaVivy 4 года назад

I'm planning on building my atx power supply as a lab bench power supply. Is it possible to use this kind of setup to create a constant current source at my load?

@magnuswootton6181 3 года назад

more ohmage, more voltage, less ohmage less voltage, its a recipe for disaster so you have to give it a maximum voltage it can be.

@gerrymcerlean8432 4 года назад

I don't think this is a cc source. A cc source should deliver the same current regardless of the load and the supply voltage.

@mark8664 4 года назад

What about using a simple couple of rectifier diodes on the emitter of an npn transistor.

@michaelmolter6180 4 года назад

Doesn’t the current on this circuit depend on the beta of the transistor? I though you weren’t suppose to use that as a design parameter?

@TheShowdown16 Год назад

Does this equation hold true for the equivalent arrangement with an PNP?

@andrewandrosow4797 9 месяцев назад

Hello! Good video! I want to tell about several problems in this circuits - what happened if supply voltage changes? Bias voltage will also changed - so, the current source will be working with an another constant current value.

@learnelectronics 9 месяцев назад

It's a simple demonstration taught in electronic texts. It's not perfect, but beginning electronics students aren't ready for a fet and an opamp just yet

@arduinocowboy3960 5 лет назад

Ed is right. It only controls current at a constant voltage! How do you design a true Constant Current driver that works with a variable voltage? Hypothetically speaking, a 80mA constant current with a source voltage ranging from 10v to 30v?

@learnelectronics 5 лет назад

Current mirror

@jwiegley Год назад

Only constant relative to a constant voltage. If you vary the voltage so will the current.

@Dazzwidd 5 лет назад

I'm afraid that's not a constant current source. Sorry to be a killjoy

@maquinas-texiles-peru 2 года назад

amigo me agradas 👍👍😁 . gracias por tu conocimiento

@johnpricejoseca1705 2 года назад

Happy birthday! ( A couple years and a few days late! :) )

@asunasposibol 5 лет назад

Hi, I really like your videos. Could you do a series of classic circuits like this?

@learnelectronics 5 лет назад

Yes

@jamest.5001 5 лет назад

I don't know why, but when numbers are substituted with letters , my brain shuts off! Sorry I missed your B.Day, happy late birthday! I had one a couple months ago,, do you have an address where ppl can send you things?

@learnelectronics 5 лет назад

Email me

@westerngodzilla 5 лет назад

Happy Birthday!

@bradleydosch8884 2 года назад

Awesome circuit and well explained, thank you! I am trying to design my own current source to use in a zero temperature coefficient application. I was using the LM334 with a diode (opposite tempcos) but the LM334 is too large for my board. Hoping to try this design out - thanks again!

@nachohaxor 5 лет назад

I always get distracted by the trucks outside where you're at. I always think they're outside of my place and realize they're coming from the video. (completely irrelevant comment)

@learnelectronics 5 лет назад

How about the trains?

@nachohaxor 5 лет назад

I don't have trains around here, so I'd expect them to be in the video and don't pay attention to them. When I hear a truck, I'm hoping its the ups guy though it's the video tricking me. Shrug.

@zwischendurundmoll3968 Год назад

Would you say this could be used for driving laser diodes?

@jj74qformerlyjailbreak3 3 года назад

Happy Birthday 🎊 Now Back To 85. 😉

@naturalmilkhoneyandzenretr9508 4 года назад

Talk to me I'm a Natural healer and RN I need help from you

@Garuda_Vigyan 2 месяца назад

Happy birthday🎂 to u sir🎉🎉🎉

@mikeoliver3254 5 лет назад

Another great video this is a circuit we all should all know deep down. Now I actually understand the math part of it. Thanks Paul you rock and have a great birthday 🎂.

@aCloudOfHaze Год назад

Gold! Thank you very much

@hnc1354 2 года назад

Hey happy birthday sorry for the lateness :)

@tonyrebeiro 4 года назад

Your video did not demonstrate, the effects of changing the supply voltage by about +/- 15% and also changing the load resistance by about, say +/- 25%. This would be a requirement in practice, because these two values are prone to change during a sequence. Thank you.

@koggism 2 года назад

That circuit is a classic class A voltage amplifier

@boblewis5558 4 года назад

Something else too. Using the PNP variation where the collector feeds a constant current out but using two diodes in the base bias chain eg 2N4148 or BAX16 Signal diodes or any typical Silicon signal diodes, with a high voltage PNP transistor this provides a great constant current suitable for testing multiple voltages of zener diodes. Just feed the zeners with the current supplied from a high enough voltage supply and the zener voltage can be read off directly with a volt meter. WATCH FOR.MAXIMUM POWER CONSUMPTION OF THE TRANSISTOR EXPECIALLY WHEN MEASURING LOW VALUE ZENERS as it's very easy at 80v supply and 10 mA to fry a small transistor being used essentially as a controllable series resistor!

@kensmith5694 4 года назад

An old style green LED is better than two diodes. The tempco of the LED almost exactly matches the EB drop of the transistor. This means the current is nearly constant with temperature. Two diodes makes for a decreasing current with increasing temperatures. On a BJT, you often hit the second breakdown before you hit the maximum power. Basically, if the voltage is over about 6V, you need to pay attention to that curve in the data sheet.

@boblewis5558 4 года назад

@@kensmith5694 like I said previously, spot on, except a green LED requires MUCH more bias current than two signal diodes, which depending on output current desired (if >> 10mA) can be very stable at

@kensmith5694 4 года назад

@@boblewis5558 The LED only needs well under 1mA to get it into its range where the tempco matches. I design stuff that is used out in the environment a lot. Tempco matters in those cases. Also things like audio power amplifiers tend to self heat a lot. In those cases, stability against temperature matter a lot. There is a slightly more complex circuit that avoids the temperature rise with supply voltage issue. You split the resistor feeding the LED into two equal ones in series. A low leakage current 6.8V Zener can then be run from the mid point to ground. Below about 15V, the zener does nothing. Above about 15V it constrains the rise of current into the LED.

@incxxxx 5 лет назад

I could not explain some mistery (for me). Namely, if you check by neon tester main socket you see - for L it lights, for N does not light. It is normal, because N line is grounded. But if you do the same using 230VAC/230VAC separator you can expect that the tester will not light on any end the secondary coil of the separator, or light on two of them, because secendory coil is not grounded and two of its ends are equivalent. But, in reality, check it (!), only one end of the coil will light the tester. Why??? Nobody I met could explain this.

@DeltaSigma16 2 года назад

This is not a current source, but a current sink.

@MalagasOnFire 5 лет назад

Happy birthday then and enjoy cup cake. Thanks for the circuit

@keeganharmon8595 3 года назад

just saw this video, so happy belated birthday to ya Paul! sorry im a lil late to the party haha. excellent example of a CC source, wonderfully simple.

@krishnachaithanya2841 5 лет назад

However this is a limitation to this, if we increase Ic value over a threshold the transistor may not remain in active region. Thus the equation Ic =(B+1)Io won't be true

@JohnSmith-ed1sr 2 года назад

you said classic circuit(s) plural. So what is the next one

@learnelectronics 2 года назад

There is an entire playlist

@Anton-sz6ef 3 года назад

Can you charge a battery with this ?

@Taran72 4 года назад

That was great! thanks for the video! HAPPY BIRTHDAY!!!! :)

@SpeedDeamon95 5 лет назад

Hmm.... This makes sense. I think I understand more now why Forrest Mims III used two transistor to switch and led/light. One transistor works as a switch and the other a constant current source?

@suhailasaba1051 3 года назад

3:49 Question: What would make more sense to call the circuit Constant Current Source having this circuit with the loud included or excluded ?

@souradipdas5109 6 месяцев назад

The actual Engineering Starts from here, A big Respect from me sir . From India

@commanderkelly1772 5 лет назад

I am just starting to learn electronics the ciruit was easy to understand but that math part of it went way over my head lol.

@stevepearson8791 5 лет назад

As a newbie I enjoy your lessons and have learnt a great deal however I'm 58 and don't understand the maths any suggestions does it really matter ?

@davidloter1670 5 лет назад

Hi , where did you get that resistance substitution box ? , thanks for sharing your knowledge

@learnelectronics 5 лет назад

Amazon

@adreq3.05 5 лет назад

The drawing a schemati diagrams i always beginn from transistor`s symbol. What is a device at left side? Where it can to get it?

@dhpbear2 5 лет назад

Another cool demonstration would be to vary the load and measure the load current! This proves that it's constant current!

@bobmutchseo 5 лет назад

how about a simple CC/CV circuit?

@mrashad219 3 месяца назад

I was going to use this with a K type temperature probe and connect the out put to a PLC. Does that make sense or am i missing something.

@emmanuelmartinez9895 5 лет назад

Wouldn't a constant current source, be always the same current despite changes in resistance??

@Spajo84 4 месяца назад

Than you sir,you are my hero!

@bogywankenobi3959 4 года назад

This is really taking the long way around, you know. It's a lot easier to understand if you point out that setting the voltage at the base also sets the voltage at the emitter - when operating in the linear region of the device.. That emitter voltage then determines the current through the emitter resistor . . . which in turn, "is essentially" the collector current and does not vary with the collector resistor.

@nazmialsaafeen 3 года назад

man you are awesome if my electronics doctor would explain like you do,i would have been much better thanks

@wasanthawimaladharm 5 лет назад

Your voice make me tired,anyone else noticed it by your self like this.

@Inquire98 5 лет назад

I promise to support you, as "best" I can 😋😎😋

@captainpugwash4100 5 лет назад

Paul, I am confused! The 2222 data sheet states hfe = 100 (300 max.) my transistor tester is showing about 260 and you are using 436 in your calculations. Why the massive discrepancies?

@learnelectronics 5 лет назад

200-300 has been my experience. I don't know why the units I had are showing so much amplification.

@MrPenguin098 5 лет назад

Happy Birthday!!! Enjoy that cupcake. 😎🎶🎶

@wellusee 3 года назад

Definitely save this one to my saved file. (Subscribed)

@vishalgaurav4411 5 лет назад

You could have woke the multimeter by pressing a button.

@stevetobias4890 4 года назад

Thank you and happy birthday

@xristost68 5 лет назад

How is this "constant" current source - if we change the Vcc, the Vb will change and the current will change. It will be constant if the R2 is replaced with zener diode for example.

@kreynolds1123 5 лет назад

Its constant current only under a varying load resistance but as us, this circuit also needs a constant Vcc.

@kb0roc 5 лет назад

You really have this down. I can't seem to just dream stuff up like you. I feel I need to google circuits. It's best to understand it. Thanks

@brocktechnology 5 лет назад

I am missing something. The current through the R1,R2 circuit is proportional to input voltage, therefore the base voltage is proportional to input voltage, therefore the base current is proportional to input voltage, therefore the output current is proportional to input voltage, which is what we started with. Somebody help me out.

@johncundiss9098 5 лет назад

You are correct, it is not a constant current circuit cause the current will vary with input voltage. If it was constant current you would be able to run the thing on 12 volts. you could put anywhere from one to 4 led in there and they would all be the same brightness regardless. This is not so whit his, if you change input voltage your current changes as well.

@dmkays 5 лет назад

Happy belated birthday and thank you for the tip. That may come in handy down the road.

@kychemclass5850 3 года назад

Happy belated birthday.

@Flapjackbatter 5 лет назад

Yes. I did enjoy that. I have never thought about this circuit configuration as a constant current source like that before. But then again, I altso have never seen a university from the inside before either. Am I correct in thinking this current source is better at regulating when the load resistance and/or impedance changes, rather than VCC changing ?

@learnelectronics 5 лет назад

Yes you are

@robnic52 5 лет назад

Thanks for the info. I am a total nube, where is the current output taken from please, off the emitter? Oops I guess the load is the output? Also is the beta the drop across the transistor? Perhaps i should watch your first video and work forward. :)

@learnelectronics 5 лет назад

Beta is amplification

@pepe6666 5 лет назад

hey man thanks. i sub'd. also i swear that was my multimeter. do you have that annoying one that turns off but beeps at you before it turns off? i mean gees it thinks its so important. i want to mod my multimeter. somehow make it know that its not important enough to disrupt my train of thought.

@learnelectronics 5 лет назад

Lol yep