Episode 1157 Let's look at some transistors and measure the current gain including Darlington's Be a Patron: / imsaiguy
Пікірлер: 51
@RK-kn1ud2 жыл бұрын
"let's quickly slap in the previous transistor before we set our LED on fire"
@cmuller14412 жыл бұрын
The gain varies a lot from one transistor to another (of the same reference) and with current, temperature, Vce etc... The only thing that matters is the datasheet and the minimum guaranteed gain in it. Also when calculating resistor values during a circuit design, it's better to use a conservative value. Measuring a transistor and then building a circuit based on that is the first step for a bad day.
@HA7DN2 жыл бұрын
Two things you can't depend on when desigining with a transistor: - current gain ('round 200 when you must) - base-emitter voltage ('round 0.6V) If you are doing something that needs some precision always include a trimmer!
@JonDeth3 ай бұрын
I would say keep in mind the traditional BJT is both a current *and voltage amplifier.* I recently configured one for high input impedance in contrast to the source, and still achieved very high voltage gain. About 300mV input AC signal, and 3.6 vac output. Bias resistors being 1 million and 100K for my divider. In contrast, running a very lossy 1.8K and 150 ohm divider, I was only achieving 4.0 vac, but obviously my current gain is massive. *It does go to show that BJT's still have excellent voltage gain when configured for high impedance.* That impedance is only about 100K, *but my source is on average 15K.* The MPSA13 and 14 obviously give me a lot more current gain, but working with guitar signals my focus is on voltage gain. I've gotten lazy with the math, but will start again soon. It's been 11 years since I was last in school for engineering lol.
@PrincePloppy8 ай бұрын
Im only 2 years into learning electronics. Great video. TY so much!!
@cmuller14412 жыл бұрын
13:00 There's another very important information to look for: the maximum power dissipation. 0.625W is not much. For example with 10v Vce the maximum current is not 200mA but 62.5mA !!!! This is with an ambient temperature of 25C. If it's in a box during summer, it could easily be 50C. With a derating of 5mW/C it's 125mW less ie 500mW max so a current of 50mA. 1/4th of the claimed 200mA. Be careful!
@ralphj40122 жыл бұрын
You wouldn't necessarily need a summer's day, what looks to be a 100 Ohm 250 mW resistor will provide an internal heater.
@plainedgedsaw16942 жыл бұрын
But that's only problem in linear mode.
@jainmanish1232 жыл бұрын
For higher current requirements I like to use AO3401 and AO3406. They have very low on resistance and switches Amps in small sot23 package
@stevenbliss9892 жыл бұрын
...and AO300, ..they are great,, and super cheap! :)
@user-cf7be9km5m2 жыл бұрын
Your lessons are priceless! If possible, about the calculation of the transistor switch and the amplifier stage lesson. Thank you.
@AB-yu2tj2 жыл бұрын
Thank you for this.
@t1d1002 жыл бұрын
A trick for young players for all types of ICs is their wattage rating. All/Most IC have a maximum wattage rating that is well below their maximum volts rating times their maximum current rating. If you max out both the volts and amps, you are going to cook things.
@t1d1002 жыл бұрын
I see that another commenter mentions this below and that they also point out that this is under the Pd (Power Dissipation) section of data sheets.
@AB-yu2tj2 жыл бұрын
Thank you.again
@RideGasGas2 жыл бұрын
I don't think I heard you mention what what the hFE actually stands for. Apologies if I missed it. You described it well, but for those interested, what I found for the definition of the letters is: hFE is an abbreviation, and it stands for "(h)ybrid parameter (F)orward current gain, common (E)mitter", and is a measure of the DC current gain of a junction transistor. I learned it as beta or the greek B symbol and had to relearn it as hFE. Actually I'm old enough that we learned tube theory first and then about the new kid on the block - transistors. FETs were mentioned as an interesting device that might pan out some day :-)
@IMSAIGuy2 жыл бұрын
Not sure if I ever knew what it stood for.
@willthecat38612 жыл бұрын
hFE is the 'same' as beta: the D.C., or static current gain. hfe is dynamic, or A.C. current gain. I'm glad to hear you didn't have to go through the H parameter model for a BJT, based on a two port network. Not really a very good model of BJT anyway, since it's a temperature dependent non-linear device. But hey, it was good math workout for the slide-rule, and Brylcreem, engineering crowd of the early 1960s, hanging on for dear life to vacuum tubes.
@fredmitchel12362 жыл бұрын
Glad to see a transistor.lesson and that you are taking a break from the Japanese scope... I look forward to seeing traces on the CRT some day...& no hurry. And that is hasn't caused too much of a loss of sleep... When HFe is wrote in little caps it implies an AC beta or cuurent gain...and I know you knew that... I am forming a little creation and will send a tiny description.... Have a great day. We used the MPS-A13 by the boat load... I will look up the MPSA14 to see whatever subtle difference it has with is little brother... It seems like there are too many choices out their and Motorola and others were never afraid to do a slight redesign for their customers and find a new niche. I think my Motorola Power datebook was the fattest out of all of them..... With so many choices ....some classics seem to be prevalent..... Maybe familiarity with the EE played a role... I wonder the single most popular transistor ever sold would be a ???
@plainedgedsaw16942 жыл бұрын
I have a suggestion for a new video. Have you heard of diode steering/ORing to power a load from 2 batteries? Basically put both batteries (or supplies) on same ground, and give each of them a diode between their positive and the load. If the batteries have the same voltage, it should be switching rapidly between the two, the faster the diode, the faster the switching, but i'm a bit skeptical about that part of it, so I'd like to see that on scope.
@frankowalker46622 жыл бұрын
Whenever I buy IC's or Transistors I always download the datasheet for them, even if they are replacement parts for something broken.
@adrianvonino25742 жыл бұрын
Nice videos, i really appreciate. I have a question regarding transistors: from what i get, some transistors are better for liniar applications (like amplifiers) while others are better for switching. Can you give us any informations as to what models of low power bipolar transistors would be best for switching, please ? I've been working alot with BC547 and lately i realised i actually don't know if it's best for liniar, switching or if it's an average transistor. Thanks alot
@BrendaEM2 жыл бұрын
Good video. I would like to see a video on DC coupled amplifiers, for, um...a function generator (ducks), perhaps something with TIP120s/TIP125, for a handful of watts, at most. Perhaps a simple Op-Amp front end, with adjustable bias, likely not the LM358, which suffers from crossover distortion. A dual-rail 15c or 18v power supply would be nice, perhaps with some of those "capacitor doubler" pass transistors. Perhaps a regulated power supply for the bases of transistors. Perhaps the out of band frequencies highs could be pulled down with caps. But of course, I have no idea how to bias any of this, and there is very little information on DC-coupled amplifiers out there. ~ On MOSFETs, I tend to put a 10k pull-down resistor on the gate to make sure the capacitor nature of its gate is well drained. I don't know if the 2n7000 suffers from this, but some MOSFETs won't shut down in any reasonable time without it. I seem to remember Afrotechmods draining one with his fingertips. [For Arduinos, a $1.65, IRL640A logic-level MOSFET with a t0-220 case, works pretty nice, up to 200V / 18 amps. Of course, 100 or 1K resistor current limiting should be used between the controller pin and gate. The IRL640 Rds is something in the milli-ohm range, which is okay for a logic-level MOSFET. For inductive loads, a helper diode in the flyback configuration is a good idea. I have been working on a circuit using them with optocouplers, when I noticed that because of the optocouplers made the MOSFET spend so much time in linear region, it became quite hot with PWM at 12v and 1A, over 10Khz. I experimented with just an LM358 Shmitt trigger, and then Comparitor, but the LM388 slew-rate was too slow--also keeping it in the linear region. So, I found some optocouplers with built in Schmitt-triggers, the H11L1M series, which I hope will allow, which I hope will be at least 16kHz PWM. Well, see.... I was even tempted to test the SN74LVC245AN class device bus transceiver as a schmitt trigger, because the square waves that come off of it are so sharp you could cut yourself on them.]
@willthecat38612 жыл бұрын
On Mouser, for 2N3904, the price for one unit is 7 to 10 times what you quoted. Some manufacturers are cheaper; but, there might not be stock. You have to buy 1000s of them to get them for 5 cents each.
@IMSAIGuy2 жыл бұрын
wow, that's a big mark up.
@t1d1002 жыл бұрын
Thank you. Great information that really helped me. What would you say is the iconic TO-92-style Darlington Pair Jellybean Transistor? The one every hobbyist should have in stock to learn and play with? The MSPA14, or something else?
@IMSAIGuy2 жыл бұрын
just use a n-channel FET Darlington's are dead
@willthecat38612 жыл бұрын
@@IMSAIGuy I like BJTs. They're the little friends I grew up with. (And vacuum tubes are like the weird uncle I never had.) But besides a few very niece analog designs, or putzing around with older gear, there's no point: the FET is king and friend. The BJT is the weird uncle now.
@uksuperrascal8 ай бұрын
Hi - Would you drive your car flat out every where? - Then why do you drive the LED at Max Current and shorten it's working life? - Also what are the components to the left across both top and bottom of your bread board supply rails they are not in your circuit drawing?
other components are .01uf caps on the vcc and gnd kzfaq.info/get/bejne/ncqkmc2JxpjXZ58.htmlsi=giYh_apaeqB2wcLf
@8-bitbitsa8212 жыл бұрын
If you do saturate that transistor, Forward current through the LED should warm it up ! Max I(fwd) for most LEDs around 20mA…
@andye20052 жыл бұрын
The higher current spec is for the 7002 device. Andy
@pukkimi Жыл бұрын
Where can I get those nice clip on leads, moreover the end that attaches to the multimeter with standard spacing?
@IMSAIGuy Жыл бұрын
hand made from parts from www.pomonaelectronics.com/ minigrabber test clip dual banana jack
@pukkimi Жыл бұрын
@@IMSAIGuy Thank you! I'll grab some next time I'm ordering some components.
@jjoeygold2 жыл бұрын
measure the hfe while warming the top of the transistor
@mr1enrollment2 жыл бұрын
note you have looking at Absolute Max ratings,...
@willthecat38612 жыл бұрын
1 ohm on resistance is nothing to write home about. It seems the through hole T0-92 style package is responsible for the relatively high on resistance, and relatively low continuous current capacity. TO-220 packaging has better performance; but it's harder to use in a breadboard. If one goes to a surface mount package, higher currents and lower on resistance are significantly better. In terms of buying a few to a dozen units, the price for the better performing SMD devices is about the same. Use a PCB adapter for breadboarding with them.
@twotone30702 жыл бұрын
I have very limited knowledge of transistor practice but didn't think 1.2ohms was a particularly low on resistance for a MOSFET and in fact the calculated equivalent Vce was the same as the BJT.
@rolfts57622 жыл бұрын
1)Thanks & 2)Question ,,,Thanks for super videos mr.ImsaiGuy :-) ,,,Question: Is it really a 100ohm, and not a 1kOhm in series with the LED on the breadboard? >..Just asking because it seems the LED survives with over >80mA (according to the video's calculation with the 100 ohms series-resistor) ..standard led's have 10mA to 20mA nominal current-requirement, pluss-minus some few mA's. //Thanks again for sharing video's to the Diy's&Engnr people. //br from norway.
@rolfts57622 жыл бұрын
..Trying to look again, though difficult to see from video, if the series-resistor is a : 'brown-black-brown' (100) or a 'brown-black-red' (1000) >>Also, it could be a slim possibility that the resistor could have been marked with wrong multiplier from the factory. >>If have time, measure the Led-resistor with your Dmm. //Thanks again, have a nice weekend over there.
@IMSAIGuy2 жыл бұрын
Yes, it is 100
@rolfts57622 жыл бұрын
@@IMSAIGuy ..>>Me standing corrected and learning something new, in regards to the >80mA trough the LED (which myself thought was unconditionally to-much)...It seems perhaps the 'impedance' on the LED must be Dynamic..? // Did an experiment at my bench here (with 100ohm resistor and Led in series,..with PSU constantCurrent limited to 80mA), and it showed that the 'voltage' over the Led stayed much lower.
@mr1enrollment2 жыл бұрын
what current does your little box test the transistor at?
@IMSAIGuy2 жыл бұрын
5:53
@mr1enrollment2 жыл бұрын
@@IMSAIGuy cannot read it but never mind
@t1d1002 жыл бұрын
@@mr1enrollment Pretty sure it reads as Vf = 1.16V. This is the voltage at which this particular IC turns on. That value may be different than what you would like to know... Are you asking what is the voltage sweep range of the tester? If so, that data may be a little difficult to come up with. But, IIRC, the tester was a project released by the developer and the Asian manufactures picked it up and mass produced it. Maybe a PIC16Fxxxx project. That kind of sounds familiar... Anyway, you can google the original project and get more information on the circuit and its operations. I hope that helps.
@mr1enrollment2 жыл бұрын
@@t1d100 was curious about what Ic the Hfe was measured at. no prob. lost interest.
@IMSAIGuy2 жыл бұрын
@@mr1enrollment oh, sorry I miss understood. I have no idea what conditions, pretty low I would guess
@barrybogart54362 жыл бұрын
Very good and timely for me. Thanks. I'll repeat you demonstration with the parts and gear I have handy. I would recommend that you upgrade your little component tester. This guy explains the upgrade: kzfaq.info/get/bejne/Z6qKetpexL-yY4U.html 73