Introduction to PNP transistors (20-Transistors)
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- Опубликовано: 21 ноя 2024
- How to bias a PNP transistor. How to deal with negative voltages. How to tell if it's in the forward active mode, saturation, reverse active mode, or cut-off. This is the easy way to handle PNP transistors.
Aaron Danner is a professor in the Department of Electrical and Computer Engineering at the National University of Singapore.
danner.group
Video filmed and edited with help of CIT, NUS.
I enjoyed learning biasing calculation analysis. This is better than text book reading. You are very clear, explaining is complete. Thanks.
Since I was a kid, I remember that the arrow points to "N". Nice. I like to revise things, and consolidate my understanding. Thank you
thank you , for over 25 years i never understood why complementary audio output stages are considered "sub optimal" in favour of npn +npn totem pole output with phase invertion on one
Yup. Can't trust those holes.
PNP I’m like dynamite, PNP I can drive a light, PNP with a power load, PNP, too much and I’ll explode!!! - from AC/DC! Rockin! 😂
How long have you been waiting to inflict that bit on the world?
Clearly you don't understand a thing... As there is nothing wrong driving a load via the negative leg.
That was so horrible, and I love it. Stealing this.
I'm a hobbyist -- learned by trial and error. I've never been scared of numbers but I seldom bother to look at them when building circuits. So long as the arrows point the right way and the currents look like they're going to be well within tolerance, my stuff mostly kind of works, since I don't build anything fancy. But needless to say, I've blown up my share of components.
Anyway, I've always stayed away from PNP because I didn't know what to do with them. A few seconds into the video I had the Eurika moment. And the rest of the tutorial was cool too. Subbed. Looking forward to learning more. Thank you!
Excellent tutorials Aaron. Having been in the electronics industry all my working life, I can still learn from your methods of these basic
Lessons on bipolar transistors. It will be great for the next generations coming through to follow your tutorials. Keep up the good work.
In the Navy we learned a way to easily distinguish pnp and npn transistors. Looking at the emitter, it’s either ‘pointed in from the perimeter (pnp)’ or ‘not pointed in (npn). That was 50 years ago and I still remember it.
I think of it like this: the base is the middle part of the transistor, so the middle letter of the transistor type tells you what charge needs to be put on it (relative to the emitter) for it to turn on.
I bet you still remember the resistor color codes little saying.
P points to N
In the Netherlands we say "Pijl Naar Plaat" which translates to "arrow to plate".
Thanks for answering my long-held question about WHY, specifically, PNP transistors are not as good/reliable as NPN transistors and why we don't typically use them in high-power applications unless we absolutely need to.
When I was a youngster back in the 70s, all the 8 transistor radios had pnp transistors. That's my first experience with transistor, and it wasn't so hard then. Now convention has changed where you draw these things upside down.
I grew up with PNP germanium transistors. When I started my career in the electronics industry I encountered NPN devices, and everything I had learned was turned upside-down. I am now used to both, and trying to get my 68 yr old brain to remember all the permutations of FETs. 🤔🤔🤔
I was very intrigued by reverse active mode operation and went on a small googling tangent. Results came up with this very specific usecase for reverse-active-mode:
Fuzz-Effects for Guitars. Running VERY HIGH gain NPN Transistor (2n5089 e.g., with a whopping 1.2k in the best case) in reverse mode severely limits their gain and reduces saturation current such that the transistor itself saturates and distorts the input signal long before clipping into the supply rails. This is said to give a more "tube-like" distortion with less unpleasant harmonics.
I just stumbled on this excellent tutorial. I am going to enjoy carching up on some reviews and new material.
07:02 "...the erros point to the right direction..." I learnt someting today, ty Aaron.
"6:20 everything could be screwed up" I like it when you talk technical
Very good. I wish we had vids in the '70s (in the USN) & early '80s -- when I was in EE school. Good luck.
Nice video...thanks for the upload.....Subbed and Liked...
As someone who has worked with electronics since my college days back in the early eighties. One piece of info I learned that is very useful is:
To find which leg is which on a NPN Transistor.....
Put the Red lead of your multimeter on a Random pin.....place the Black lead on another.....note what you got....Assume OL on the Multimeter....
Place the Black lead on the remaining lead.....note what you got....Assume OL on the Multimeter....
Do this again but move the Red lead to another pin.
You might get OL again but if you get ~0.6, leave the Red lead on this pin and move the Black lead to the other pin.....
If you get a slightly higher reading then you can safely say the Red lead is on the Base and the Black lead is now on the Emitter.
The remaining pin will be the Collector.
You have to be patient and take accurate readings because Base Emitter voltages change dependent on the Transistor type and can be noticeably different or slightly different.
Your reading combination will tell you if the Transistor is NPN or PNP......
With practice, this method will be helpful, it has served me for years...hope this is helpful......
Thanks for the amazing and clear content, subscription earned!
Thank you. Never knew about the reverse active mode.
If you look at textbooks and schematics from the late 50s to the late 60s you will see a lot more PNP transistors. The behaviour of PNP is more similar to the triode so they were more comfortable with it. That may be why it "blows" away people today. "kids these days" are not used to thinking of negative rail as anything but ground; I have seen some struggle with differential supplies (e.g. +15 and -15).
Can you Make differential supply make sense
I had to replicate a 1950s circuit that controlled slave clocks, it used a PNP transistor in a TO-3 package. I didn't have one, but had lots of NPN of a similar spec, so I mirrored the circuit. Still working 15 years on.
Everyone had 2n2955 PNP TO3 case.... Surely you could have found one..
You could have explained all the cases by superimposing the vcc= rc x ic + vce curve on the transistors operating curve of the manufacturer instead of drawing on for 20 minutes and no doubts cleared
This channel is amazing!!!!
A few years ago a professor explained to us an “easy way” to identify each part of a BJT symbol, since the emitter is called that because it is the one that “emits” the charge carriers, which will be holes in PNP or electrons in NPN. Then he adds, so remember, the emitter is the one with the little arrow.
I would love to see then a pure/only NPN transistor H-Bridge. Is it really that simple to just trun the NPN transistor around to get the negative side working?
Thanks
An unexpected but useful lesson in my daily YouTubing
"reverse active" mode --- I ran into this because the 2n2222 part I bought was from OnSemi and the OnSemi data sheet for that transistor has the leads labeled backwards and my circuit didn't behave as expected, took an experienced electrical engineer to figure it out (I'm a software engineer and would probably never have figured it out on my own). turns out the OnSemi data sheet is opposite every other manufacturer's data sheet for the 2n2222 part.
pinouts can vary on TO-92 case components
@@davidconner-shover51 are you sure you read my comment, I'm not claiming all TO-92 component are E-B-C, I'm saying all 2n2222 are E-B-C, my OnSemi works correctly when I wire it as though it is E-B-C, in spite of the fact that the OnSemi data sheet says its C-B-E, opposite what all other manufacturers of 2n2222 say.
@@MostlyIC Over the years, I've run into quite a few documentation misprints
I had some rather expensive equipment that went out gloriously in the past, there was a labeling misprint on a known part, the new guy didn't know it was a misprint, or thought they made a change.
The manufacturer tried to void the warranty, until I sent pictures showing the mislabel. oops.
Yes, having the pins reversed is rather problematic
Thank Dr Danner, I was a Mech Engr and worked is systems, Medical Imaging, Factory Automation, Robotics Assembly etc etc. In retirement i have pulled out my old (1950) train set. I was determined to update it using IOT, why not that should be fun. Oh my, Motor control with Transistors is giving me such headaches. I buy circuits that work but I have no idea why. And when I want to tweak the performance I am lost at which way to go. I tried to listen and learn but I must say it is very hard. Do you have any practical applications of motor control with braking? I have a mini DC motor 3.5VDC that i want to make Puff Smoke on the engine stack. Timed to the drive wheel rotation. So I need a burst then stop, then burst then drop. The burst is driven by a sensor, but the Brake was design to stop the motor when the puff trigger pulse is off. But I am getting so much coasting there was no stop of smoke between puffs. Its a very simple and the circuit i was given is very simple but now I need to tweak the circuit. ??????????? No idea where to go to decrease or increase volts. The originator suggested dropping one resisitor from 500 to 100 ohms, and it helped. Amazing, No I am looking at the fan blade weight. It this anything you would have information of a link to a lecture that might help me to get this logic sunk into my grey cells. Thank You, Dennis
Great video thanks!
Very good lessons. Will you be doing MOSFETs next?
? Are they something new I thought we had had them for 70 years?
When calculating the base current in Forward active mode, don't you have to consider the voltage divider current on the base side?
I wonder the same thing
Yes, but actually no - base current will move the divider point a bit, but its not that important for high betas, for low values - yes you need to take it into account.
@@VEC7ORltbut that’s just adjusting the voltage division. What about KCL for the entire resistor series, 2 x 10K ohms, with 9V supply? I don’t understand why the other 10K is ignored? I(b) is the base current but why is I(1) the same?
@@soloflo what other R 10k?
Its an approximation either way or do you want to solve for ALL junctions, nodes, currents and voltages?
Didn't he do that? 0.45mA compared with .038mA base current.
Great, thanks alot
Can you tell one thing? Give typical voltages on the ic vs Vce curve. There is a sharply rising part initially and then plateaus of. Where is 0.7 volts on this curve- at the origin before it takes off or where it plateaus off? , for a given Ib. Everybody takes 0.7 volts without getting into the saturation aspect.
Secondly in the first example of forward bias case the Ve and Ib will remain the same even if you took Rc and Re as 10k instead of 1k. Is that believable? In the 1k case the operating ppint will be on the plateau region ie saturated. In the 10k case the operating curve will cut the Ic curve on the vertical stretch meaning Vce in the vicinity of 0.7 and possibly several volts in the 1k case
thanks
Hi Professor, please if you could, teach us about rectifier firing circuit for both single phase and three-phase rectifiers, from synch circuit to gate pulse to scr gate. Thank you.
Where were you when I was in college?
transistors are diode over a layer of n or p channel material. if diode conducts transistor will be open. its simple.
I use PNP transistor with open collector cercuit they can activate 12v or 24v charge with 5v logic .
This design will work, but it's not recommended. If the transistor burns, you may have 24 V running (thru a base resistor) into your 5 V electronics. It's better to use an NPN transistor on the 0 V / GND side. Or use a ULN2003 or similar.
Here we go boys and girls - Remember the ol' NPN transistor ? Well now, reverse the polarities on the bias voltages, point the emitter arrow out (remember "outies" vs "innies" ?) flip tha switch and here we go. Any questions ?
Don't say beta for current gain...it is Hfe in all the datasheets.
2:55 "Holes" do not "move", in a SOLID, atoms are fixed, nucleus does not "move" and they are the positive part. No. When an electron moves away, the atom gets an excess of proton and thus, becomes an area locally positively charged, a "hole". When an electron comes close by, it becomes trapped, and the "hole" disappears. So, if there is a hole at point A and then later on, disappears with another hole appearing at point B, the "hole" has not move from A to B, the hole has not visited the middle point between A and B, and, in face, nothing says that it is the same electron which is implied. The holes do not move (the material is a cristal in a solid), it is electrons (for a solid) which move.
I don't understand why it's called the emitter when it's the terminal that collects electrons.
As a memory aid, you remind us the emitter always labeled with an arrow.
If we don't have simulation available, how can we solve a system with non negligible base current?
There is an older standard called "conventional current". They put the emphasize on the "holes" which are the positive and empty spots. So think in terms of positive flow instead of electron flow. Then the symbols make sense.
@@CrispyCircuits thanks. Just like the symbol for diode, the arrow points in the direction of conventional current.
Harris Joseph Garcia Michael Clark Matthew
Ahem ...
IF:
the diode formed by the base - emitter junction is FORWARD biased,
as we can observe the FORWARD voltage drop.
we know that this diode is N-type at the base
and P-type at the emitter.
THEN:
for a forward voltage drop to occur in this case,
electrons must be flowing INTO the base junction.
hmm?
It's 'conventional current'; used in schematic comprehension but the opposite of actual electron flow.
Technically you are right. But PNP transistors were originally used with a negative supply rail, so your schematic is upside down. Drawn like that it just causes confusion.
No.........
"No" what?
I don't care if a lot of students don't like these that was unnecessary chatter just explain PNP go right to it you have way too many scenarios words of advice emotional attachment we are looking for facts about an electronic component not back stories of your childhood or what happened in your classes to another person learning we don't care. Good luck in trying to adapt your thought processes thanks for trying cheers brother