Transistor Impedance Matching
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- เผยแพร่เมื่อ 19 มิ.ย. 2024
- Gregory explains impedance matching of a transistor, showing the impedance transformation on the Smith Chart.
The Smith Chart is explained and used to help the design of an LC impedance match network, to match the input impedance of a BJT transistor.
Video showing what is impedance matching:
• Impedance Matching Basics
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00:20 - General impedance matching
02:20 - Why impedance match a transistor
05:02 - Transistor input impedance
06:50 - The Smith Chart
09:50 - Impedance Match Network design - วิทยาศาสตร์และเทคโนโลยี
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i wish i had the same enthusiasm for life as this guy has for impedance matching
hahahaah
I have seen similar demonstration of Smith chart impedance matching many times, but this is by far, far, far the clearest and most engaging presentation ever!! You're a genius :) The only thing missing was a P vs Rload graph at the start to show why max. power requires matched load, but I'm sure most people know that anyway.
Thank you!!
The most clearest explanation about smith chart that I ever seen. Congratulations
Thanks, Fabio!
Absolutely incredible - this is my first patron channel - I struggled with smith charts in my EE program
Welcome!
Love way you are explaining stuff. Clicks so well with me. Thank you for providing these videos.
Wow, once again you present something I've read about, and struggled with, and with one simple comment you bring it all into clarity. I don't think I've found anyone who explained that the cartesian plot is transformed into the circular form of the smith chart. I've just seen the Smith chart presented as-is. Now, as I watch the video, I imagine how the transformations look back on the cartesian view, and everything is making sense!
Thanks man!!
Excelente erxplicacion de como usar el diagrama de Smith!!
Gracias por tu trabajo Gregory
brilliant Gerg. thank you, another gem video.
Fantastic video! Really great work! This model of representation and modeling takes us to another level. Leading us to imagine even in materials engineering concepts.
Amazing !
very good video, look forward to a video describing how to determine transistor base impedance
Thanks!
Hey! I was cycling yesterday thinking about it, your explanation give me a clear idea about this subject, thank you !
Glad it was helpful!
This by far is one of the best explained video I have watched explaining impedance matching a transistor. Simple, concise, and to the point. Really well done. First time bumping into this channel and subscribed immediately. Keep up the great work!
Wow, thanks!
Excellent teaching method keep up the good work👍
🤘🤘🤘
Just ran across your channel, and the RF stuff is right up my alley so we SUBSCRIBED!!!
Looking toward more RF as well as exploring your back-catalog!
In my younger years, I became fascinated by radio and analog electronics but it was digital where I ended up making a living.
So, I am retired so I have collected some test-gear (missing a sweep-generator) and want to dust-off all the analog and RF stuff and do my own TX/RX designs.
73 & Thanks for all your efforts... 😀
Be welcome! 😁😁
Sometimes his accent is tricky to understand but the content is very helpful!!
Glad you think so!
i am currently going through the art of electronucs and the first 2 minutes of this video makes so much sense now there is an exrecise in the book that calls for proving that the maximum power supplied by a non ideal voltage source to a load is when r=R (internal = load)
That's great!
QUE PIJE VIDEO! Really helpful and insightful. Greetings from Central America.
Thanks!
Great content as usual! Just one question. Is ~36 ohms a typical small signal base-emitter resistance for a BJT in RF applications? Ive not yet seen one that small. Seems that would roughly equate to a base DC bias current of about 720 uA and that seems pretty high compared to what Im used to designing.
Thank you Ryan! Indeed 36 real part is a little low. Sometimes I consider 35 ohm as the complex Z for small signal at 500MHz.
Works well when matching a common base using a series 15ohm resistor.
Saudades dos seus vídeos em português, quando eu consegui juntar dinheiro para comprar os seus cursos, vi que não existe mais, vídeos bloqueados... que pena, você me foi um dos motivos para iniciar engenharia elétrica... abraço.. agora vai ser um motivo para aprender inglês kkk
Não acompanhou o lançamento do RF ESPECIALISTA - O CURSO? Ainda temos vagas com acesso ao grupo whatsapp do curso! cursoeletronica.com.br/
Excelente explication. Thanks.
You are welcome!
Thank you Gregory
🙏🏼🍺
Hi gregory. Good video. Are there any networks methods that allows matching on multiple aribitrary wide- bands and not just a single frequency?
Very interesting question.. we would need some kind of a two port diplexer network 🤯
Mate you are one of the best to explain and teaching complex Topic like this one.
Thanks to share your knowledge.
Subscribed!
Greetings from New Zealand
Thanks my friend, welcome to the All Electronics Family
Excellent video Gregory, I have seen many of matching impedance circuit at one specific frequency but how can I design a broadband matching impedance for example for TV signal of 6MHz bandwidth
Thank you, Sergio! In a next video I will show how to use the Smith Chart to accomplish higher bandwidth.
Nice work.. Keep going!
Thanks!!
Thank you for the video, it is darn near exactly what I was looking for.
If I were to suggest adding things, it would be to give the part number of the transistor you are using, and to show how you got the base impedance. I looked at the datasheet for the transistor I want to use and low and behold it has a piece of a smith chart showing the resistive and reactive components at a few different frequencies. There seems to be a trend so I think it is safe to interpolate a bit at least between the marked points.
Thank you again for the video.
Excellent!
Hi, I wanted to ask - you said you measured the input impedance of the transistor, do you have a video showing how you did that? I know RF transistors the manufacturer usually provides the "S parameters" which kind of give you this info already but I'd be interested in knowing how to do it. Would it depend on the emitter current somewhat though I would think? Seems like it would be a combination of emitter current/beta and the input capacitance in some way.
Yep, it depended on the physical construction and biasing condition. Some manufacturers give the S parameters in the datasheet and in some cases you need to measure it using a VNA.
That was excellent!
Thanks!!
Great video
Glad you enjoyed it
your tutorials are always amazing, please can you do a video on how to calculate the R and xc impedance parameter of a transistor amplifier
great video!!! Amazing informations! i'd love to know what technique you used to measure the input impedance of your transistor. Also, could you discuss how to measure the output impedance of the transistor?
I was writing the exact same question.
Thanks guy! I'm planning that for the next videos!
@@AllElectronicsChannel Will be very nice to see this measurements demonstration ! Looking forward to that . Thanks a lot !
@@AllElectronicsChannel Excellent videos! I'm wondering if you got around to making a video explaining how to measure the impedance of the transistor. Could you do it with a regular VNA, for example?
Very nice way to make us understand...you make a lot of efforts to create such nice vedios.
I also listen old school people..they talk a bit slow..that makes us understand better...i wish you also try talking a bit slow...
Thanks a lot!
nice vidéo :)
Could you please make a detailed video on Broad band rectifier and its impedance matching?
Tank you!
Hello Gregory. It's very good video. You have to say about S parameters of a transistor. Every microwave semiconductor has a datasheet with S parameters. If you know S parameters you can to convert in Y or Z.
Thanks Dinitriy!
Excelent
Hi, can you do a Video about calculating with the j capacitance and so on?
Your video made a clear explanation of very complicated subject; however, what you missed to point out at end of the video was to do the calculation to show that 50 ohm input resistor was looking at near 50 ohm output resistor. And if audiences saw that maximum power transfer of having 50 ohm output resistor was done by your Smith chart, I am sure they would had been more impressed.
Yep! Thanks, I will revisit this topic someday
Thanks!
Welcome!
Excellent video, could you please make videos on switching power supply control loop??
Of course! I'm planning it hahaha
6:17 how did you do to calculate the parallel of 36 ohms and -266j?? to come out 35 -4.8j?? what formula did you use? do you also make a video to find bjt entrepreneurship as you say on the video?
You only need to use the default parallel equations !!
@@AllElectronicsChannel ok thanks
@@AllElectronicsChannel
Yes, enjoyed the video very much. Just dropped in here for the first time so I am curious to know if you guide on audio amplifier output stage design: Class AB, class D, and so on. Exactly on the same lines as in here & why a component is added in the circuit (Impedance matching circuit) and deriving the component values (the part that I'm exclusively seeking).
Please make a video on amplifier stage coupling (if not already made) and upload it. I Shall be very grateful.
Thanks once again for making such a wonderful video.
Hi man, thanks! I'm not the best at audio amps. Search for the channel KissAnalog , you will find a lot of good material there !
Please make a video using your vintage vna to characterize the transistor
So many video ideas! haha
Please explain how do you calculate the values using the frequency.
Default equations for capacitor and inductors reactance.
@@AllElectronicsChannel video wood be helpful.
Hi! 3:05 I do not understand why maximum power transmit means, maximum voltage at the base of the transistor. If the input impedance of the transistor is much higher then 50Ohm then almost all of the generator voltage will appear at the input of the transistor. May I have some clarification here?
No, you are right.
But in your setup the generator would no be outputing all the available power, all the power it can output.
Matching the generator to your high impedance transistor would generate an even higher voltage at the base, that would deliver the full available power of the generator.
Please engr my problem is how do I know the input and output impedance of transistors or I will used transistor datasheet thanks
A lot of times the only way of true knowing is measuring with a VNA
This is a great explanation for RF student. My question is how we calculate gain in Rf amplifiers using bjt transistors? I also follow You on instagram and you are doing great job. Keep up the good work. If you can also tell me where to find out more about calculations of RF amplifiers using impendance matching I would really appreciate it.
Exact gain calculation is a difficult job. In my home projects I always prototype the circuit and measure it.
@@AllElectronicsChannel
So lets say you are building Xtal collspits oscillator would You be able to calculate input impendance of crystal and all biasing resistors and load is simple wire antenna? Im trying to build simple transmitter and receiver but no one even can explain exact impendance of simple wire as antenna. Anyway its very interesting stuff I would be able one day to learn it all I would put it all on TH-cam like you 😃
In case of the transistor, the maximum power transfer law doesn’t apply. Usually we deal with signal voltage here. Therefore we try to extract (or drop across the transistor input port) the highest possible voltage. We should consider it as a voltage divider circuit. So, the transistor’s input impedance should be as high as possible. We don’t match impedances there.
Wrong 😁😁.
Good morning sir,
How can i know or calculate the in and out impedance of npn transistor for A class rf power amplifier and which information can help me in datasheet of the component can help me?
Thanks
The best way is measurement.. For the output matching, usually we make a load-line match. Take a look on the channel, I have a video showing that: How an amplifier works.
@@AllElectronicsChannel thank you sir for the responses
So If I understand it correctly when i would like to receive a very weak signal which would be kind of very weak source of the signal only what i can do is to develop an impidance matching network so that I won't loose much from that very little power I have from the signal received right?
Yep. In the end, you are always matching the impedance - to preserve the relation of the signal at a maximum, when compared to the noise. Take a look at my video about Noise Figures!
Thanks for the answer. But there is another thing that I can't understand. You say that your source has 50 ohm of impedance but what about if I build a receiver from a schematic and they say that a piece of wire 35 cm will be an antenna and then there is a 10 pF capacitor and then a regeneratove receiver circuit so in that case how could I know the impedance of the source signal? What if it changes, sometimes I can have my transmitter closer or further or weaker signal but I have no idea what impedance actually I have from my simple wire antenna point of view 🤔 Maybe my signal is weakend by mismatch and I don't even know it. There are a lot of things that are not answeared in books :( But when I grab a bokk for University there are a lot of equations which are not very usefull right away. I mean they are important but they don't explain the natural behaviours of things , only an ideal world.
Sorry for ortographic faults but I am writing on my mobile phone 😅
This is why I don't like those so called TH-cam tutorials etc. I get never an aswer for my complicated questions. Ok there is an a swer for a basic stuff but never for complex subjects which indicates that nobody really cares. It is only about how many people view the channel. Nobody cares about the knowledge being tranaferred...
Just wow
😝😝
Hi i made a common emmiter amplifier for 200mhz signal with 2× gain
I can amplify a 50 mv p-p to 100mv p-p but I can't do it for 2v to 4v p-p
Why what values should be change???
Hi! I have a video called how An amplifier works, take a look. I show how to optimize the output impedance to have maximum output
@@AllElectronicsChannel thanks
Great tutorial! You really make this concept much easier to understand. (Sorry to be the 778th like ruining the lucky 777 likes.)
😂😂😂
Thank you for the great explanation! I find the excess of cuts a little bit distracting … but it might be only me…
No worries!
1:00 yes you can. You can add a resistor at the output of the power source to increase its impedance...
If you have a 75 line and load with a 50 source, you can just add 25 ohms. Yes, I know it will reduce the signal and efficiency...
A resistor in series with the power source is a load.
Muito bacana, Gregory (acho que é assim que escreve). Acabo de deixar três visualizações e três likes.
Thank you.
I am not an expert in this topic, but could you explain what happenen if the input impedance is infinite. Is the power delivered zero?
Yes. In this case, the transistor would behave like a "voltage sensor". It can be model as this for lower frequencies (< 10khz?)
Can you do a video explaining conjugate matching?
For conjugate matching, you present an impedance with oppose reactance, so the reactance of the source cancels the reactance of the load.
@@AllElectronicsChannel Well yeah... but when and why would you do that?? A real-world-ish example? Reflectionless matching is the only case that really gets talked about. Conjugate matching maximizes power (of which reflection less is a special case). I've only heard conjugate matching explained in academic terms or as you did above, but I don't understand the application.
@@jonboro2000 You are going to do it every time. In this example of the transistor, we are doing that. If you calculate the admitance looking into the inductor of the matching network, you gonna see the conjugate of the transistor admitance.
@@AllElectronicsChannel Your last commend was helpful/completed my understanding. Thanks!
The maximum power delivered will occur when I short circuit the power supply!
😂😂😂
Hey Greg could you explain implemention this circuits in the real life? I don't understand about the RF stuff but I would like understand a little bit more. RF is a mystery like a black box, I know GSM, 3, 4G, 5G, Bluetooth but I cannot to link your videos and that technologies, sorry.
What do you think is the gap on your knowledge?
You must have spent 3000 hours to edit you raw material to this video. 🤣
Excellent result.
Nicely explained! I just don't get why the vid has been cut like that ..
Hahahahahaha
How would you do it mathematically without smith chart? Take conjugate ?
For simple networks the math usually is just describing the paths and distances in the Smith Chart
@@AllElectronicsChannel Ok, what is mathematical solution? not smith chart
@@AllElectronicsChannel Do you know the actual math?
Search for LC network impedance match
This is very nice, guys! It could have been even better if you pronounce 50 as "fif-tee". In your other videos, 'fif' caused a bit of confusion when you actually mean "fif-tee".
Thank you! I will improve that.
My maternal grandfather father taught electrical engineering at Rock Island Arsenal after turning down an engineering job in Florida that would had possibly left him a multimillionaire at retirement.
Wow!
At 1:56, you use the wrong resistance when calculating the power delivered to the 30 ohm resistor. You use (0.168^2)/50 for 0.0005 W. The correct calculation is (0.168^2)/30 for 0.00094 W.
True, thanks!!
Crystel clear explanation
Thanks!
I get delivering maximum power via a complex conjugate matching network but I don't understand your explanation that it produces maximum voltage across the base emiter junction of the transistor. Max voltage would occur when the input impednace of the transistor is many times the output impedance of the source, ie impedance bridging as in audio systems. With impedance matching you are only going to get 1/2 of the source voltage across the transistor. So why not jack up the tranistor impedance to be 10 times or more of the soure impednace to impose more voltage across the transistor? After all the signal inteligence is the voltage waveform, then if you needed more current follow up with an emitter follower to amplfy the current ?
Hi man! I'm glad you make this comment. This is a common misconception that a lot of people do, I also did many years ago.
You are right.
But, all breaks a part when you realize that a real transistor has a finite impedance, that cannot be changed.
So, the best you can do is to match the source to what the transistor impedance is.
@@AllElectronicsChannel Thanks for the reply, I am not getting it. For reference I have an Electrical engineering degree from an ABET acredited university, although my concentration was in controls, I have also been a manager for the last 10 years so I am rusty, I am also an extra class Ham licensee, hence the intrest in this topic.
Take the CE configuration, the input resistance is a function of the biasing network and emitter juction (re) which is a function of the transistor Beta and temperature or another word, so basically Rin = R1//R2//re, it can be a little different if there is an Emitter resistor RE and or a bypass cap. But in general the input reisistance is many 1000s of ohms. None of these componets are frequency dependent so what is driving down the transistor impedance ? What is the high frequency model of the tranistor ?
Haai brother😀😀😀
🥳🥳
It has not been clarified when we have to match impedances. In many cases it’s better to maximize the efficiency or the load impedance
This is a good video that has more explanation of impedance matching using smith charts. i.e. how to know what direction to go with L/C to get a match. th-cam.com/video/IgeRHDI-ukc/w-d-xo.html
dude, I was happy working with pure dc, making some power supplies, why I clicked here ?
Hahahahaha welcome!!
sorry to many jump cuts, and repetitions. made it hard to follow
Welcome!
Good content, but please less intense/less coffee haha, it's stressing and the "shouting" makes it hard to focus.
Hahahaha
your Audio with all the pauses edited out, is unbearable to hear,. Why do you do that? To make sure people watching get no opportunity to leave? Its horrible.
The audio is indeed appalling, but the explanation is outstanding! Hope you'll be implementing the feedback in future videos.
I can't stand this. Work on your presentation dude.
Thanks for watching 😁🤩🤩
Way too many edits and cuts.
I say he should give you your money back.
you need to make a video of how to characterize a transistor? how do you determine the input and output impedance of a transistor at a specific frequency say 100MHz. theory is not too hard to understand but the practice for people who design and build circuit is equally important.
Nice vid, but note that the 50 over 30 divider delivers (168mV)**2/30=0.9mW
Concur. 0.9 milliwatts is less than 1 milliwatt.
OK I understand now. To match the fift ohm, I need a serious capacitor. So no joking with the cap!
😂😂😂
If only he could learn to say 50 ohms and not 5 ohms and its a SMITH chart not a mif chart.
😜😜😜