#118
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- เผยแพร่เมื่อ 6 ก.พ. 2025
- This is a basic tutorial on PIN Diodes, with some examples of how they are used in RF switch applications. I previously published a video that introduced the topic of how diodes can be used as switches:
• #82: How to use a Diod...
This video takes this a step further, discussing the unique characteristics of PIN diodes and how these characteristics are used for switching large RF signals. The unique ability to have the resistance of the diode be adjusted by changing the bias current can be used for other applications such as variable attenuators, modulators, phase shifters, etc.
In the video I state that PIN diodes aren't suitable for fast switches. What I should have said is that PIN diodes aren't suitable in applications that require fast turn-off characteristics when reversed biased - such as rectifier, detector or mixer applications. PIN diodes do make excellent fast (relatively speaking) RF switches.
Here's a followup video showing some 3rd order IMD measurements vs. bias:
• #130: PIN Diode 3rd or...
The Yaesu FT-7800 Repair Log videos that inspired this tutorial:
Part 1: • #116: Repair Log, Part...
Part 2: • #117: Repair Log, Part...
A copy of the notes in this video can be found here:
www.qsl.net/w/w...
Even 11 years later this was very good to learn!
I watched this again and learned even more. Thank you.
I don't know how you do it, but you put so much useful information in such a short and understandable video. Thank you!
You are simply GREAT: a GREAT teacher in a GREAT lab. TNX!
Intersting; Finally understand what a PIN diode is used for !
I am a long time subscriber to your channel. Still finding 10 year old videos that are super educational. Thank you.
You know sometimes you just find the right video, made by the right person, and everything just goes up to an other level, that's what I have experienced several times on your channel, including this video! :-)
A great explanation of the PIN diode. Thank you so much!
This is how you understand electronics. This stuff is worth hours of meticulous reading from books. Thank you!
Aged 15 or 16, I designed PiN diode-switching into a Plessey SL600-series IC based HF transceiver which worked essentially, and ended up being very similar to a renowned G3TSO design, though I never understood the 'charge-carrier-bucket' you describe so clearly.
Excellent series of videos and amazed you take the time to build the jigs. I have subscribed.
Very informative video. I used this technique in my patented TV Pedaler® product but I never fully understood how it worked until I saw your "bucket of charge" explanation. Thank you!
Thanks w2aew any time to want to learn something I will choose you're videos....
You have helped fill so many gaps in my knowledge from things I never learn't properly at college. The five year one day a week City and guilds course my company sent me on was still teaching valve theory alongside transistors in the late 70's.
As a home project, I once built the 1/4 wave line PIN switch into a 2 meter transceiver, to switch between transmit and receive without an aerial change-over relay, but never understood how it worked until now. From memory mine consisted of at least two 1/4 wave lines and at least four PIN diodes, but memory is a bit hazy now.
Thank you for these wonderfully explained videos. For me the electronics hobby had died about 15 years ago when computers started to do everything far better than things I could build and hence little point building things any more, but your videos have reignited my interest. Thanks again.
Howard UK
Such a helpful video, thank you for explaining the quarter wavelength property. Little tidbits of knowledge like that help a lot in understanding the full circuit
All very clever. This is a completely different area of electronics to that which I'm familiar with. And so well taught too.
Excellent! Believe me, as I have > decade of teaching experience, you are just great!
Thanks you so much for all this very high quality content, you are the one with a clear signal and low noise. Thanks again.
Better than great!, you do have the skills to transmit your knowledge, that's so dificult for so many teachers, thank you!
I had never heard of a pin diode but you answered all the questions I had about it. Well done video.
Another great video and this time RF. Started out my career in consumer electronics with the old vacuum tube superheterodyne radio receiver with the old air tuning capacitor and the local oscillator operating with an IF frequency of 455KHz. Old monochrome black and white receivers which every home had supported by four legs etc.. While serving in the United States Air Force back in the late 70’s and 80’ s maintaining and servicing Radar transmitters and receivers enhanced my experience with RF however I had never heard of pin diodes. Excellent job in explaining the theory and practical applications as well as visual aid of an actual circuit of how pin diodes are used in in the isolation of a transmitter and receiver circuit.
The oscilloscope displays of the phenomena being discussed are very helpful. Many thanks for taking the time and trouble to prepare and post these videos.
I've used TX/RX PIN diode RF switches in the past, but never really understood how they worked. Thanks for a great video.
Simple and practical explanation, hard to find in literature. Thanks a lot Alan !
This was a fantastic video.. These are amazing little devices.
Thank you very much for your excellent done videos. This is the kind of learning i love, by practise step by step testing seein the result and readjust to see whats result after chaning. Great done!!! all the best
Another brilliant explanation of something I haven't previously understood properly. I've now got a backlog of projects to try these circuits myself!
Best tutorial on pin diodes ever!
Thanks a lot! 🙂🙋♂️🇧🇷
Wow. I really enjoy and learn from your teaçhing. We're house electronics teacher before. I haven't seen a teacher demonstrate theory and show the test like you do.I once had a excellent teacher back in high school who thought me well but you are awesome. Keep up the excellent job. You have a teaching gift. I am getting baçk into electronics. Your teaçhing really helps. God bless you buddy.
Thank you - I am glad you enjoy my videos!
Hi Alan, another great education piece, I always learn something new when I watch your tutorials - thank you.
Thank you for the excellent lecture. You have a talent for explaining circuity.
Fantastic tutorial on PIN diode! I don't do a lot of RF but when I see a PIN diode I'll definitely have a much better idea of what it's doing there.
As a former teacher, I recognize your excellence! Thanks.
That was an amazing tutorial about PIN Diodes - I love the application of high power high frequency switching applications.
I really enjoy your presentations on RF applications. Fantastic explanation. I love watching your practical experiments. Thank you.
thank you for contributing to everyone out there Alan , Regards from VK3
Excellent video. I’ve come to love my Elecraft rigs and the quiet nature of my HR 50 ATU with the QSK board, but I never really understood how PIN diodes worked and certainly not how they worked in place of relays (such as the noisy ones in my IC 7300). I understand the mechanical nature of the the relays, but never understood the complexity of the PIN diodes. Now I know, thanks for yet another awesome video. De W1ND.
Very interesting tutorials, now i love more and more your vids, especially RF stuffs.
Thx Alan
The intrinsic region is neutral; it stores no charge. p and n carriers diffuse into the intrinsic region and recombine. The diffusing p carriers leave behind a negative charge layer in the p material and the diffusing n carriers leave behind a positive charge layer in the n material. These charges generate an electric field across the junction that balances the increase in entropy from diffusion. The larger plate separation REDUCES the capacitance and accumulated plate charge (Q=CV) relative to a pn junction. Additionally, the increased junction volume greatly increases the probability that a photon will ionize a p-n charge pair before passing through the volume.
Thanks for explaining a pin diode ,I have known of them for years but never used one and have an idea or two or recurring ideas over time.
Hi W2AEW , I request you to make a video on RF Tuners which are used to characterize High Frequency & High Power RF Transistors(GaN) , what I meant is load pull analysis(you have already done amazing tutorials on smith charts) , by the way you are one of the best instructors I have ever met in my life
and actually what I observed in you is that the thought what comes in your mind , and what you talk or explain and later what you do on the bench are in unison and here in our culture in india we call that as TRIKARANA SUDHHI which is a rare quality , kudos W2AEW , it is always fun to watch your videos which edify
Regards Bhavani Sankar Appalla
I can add "load pull" to my very long list of future topics. Thank you for your very nice comments!
Wow! Great crystal clear instruction ! Thanks!
Alan: Thank you very much for this video on the PIN diode. Many questions answered!! I never encountered PIN diodes until I built a 40M transceiver which uses them. When I went to trouble shoot the circuit I saw just how far behind I've become in the electronic field! Again, thanks for the tutorial. As usual, one of excellent quality!!
Al - K8AXW
I never thought much about the TR switch as explained in the video.. really nice video, thanks for sharing all these insights.
So fun to learn, most important i been thinking long ago that i did well grasp this concept well but actually did not fully understand.So simple to learn when teacher really understand theory and practice.
You should teach university professors as well how to teach.
Definit. would go trough all your videos as i saw few others as well and all are excellent.
Real treasures!
Thank you.
Great video Alan. I wasn't aware of these diodes and didn't know about the 1/4 wavelength property of inverse impedance, ingenious way to chose between Tx and Rx using minimal components.
w2aew you are great in explaining the PIN diode with practical demo. I was searching for this type of video to get a full knowledge on PIN diodes. You could have informed some of the technical names of PIN diodes readily available in the market. Many thanks.
13:09 So , Although it has ony two Pins
If it act like Transistor switch linearly respect to the Bis current, can it be also use as Amplifier like instead of fix current bise what if i place signal current to its bise !? Will it linearly Amplifi the input signal ?
I was looking for a good explanation of how pin diodes are used as switches and this helped allot. thank you
Thanks. Enjoyed the video very much. My goal was to learn how PIN Diodes work and you made it quick and simple. Good show.
Thanks Alan. That's interesting. All the times I bought all kinds of diodes, I don't remember ever seeing any PIN Diodes.
You are truly awesome educator! Thanks for this great video! I wish you can do a video on antenna switching for direction finding; a feature available in BLE 5.1
This is an excellent primer on using PIN diodes in RF switching applications!
Excellent tutorial! I have advised my Uni students to view it.
Just the explanation I was looking for. To bad you didn't include the attenuator construction itself yet but I guess that's something I should be able to figure out myself!
This is so interesting. At that particular RF frequency the transmission line of the scope is 1/4 wavelength. And at that wavelength the opposite ends of the transmission line have opposite impedance! Is this only true with 1/4 wavelength or also true with multiples of 1/4 wavelength or even at any other wavelength?
The impedance inversion (around the system impedance) occurs at frequencies where the length is an odd multiple of quarter wavelengths long (1/4, 3/4, etc.). At the even quarter wavelength (1/2, 1, etc.), the impedance seen at the input of the line equals the impedance seen at the far end.
@@w2aew That is great! Thank you!
Very good tutorial on the PIN diodes! I am spending quite a bit more time on TH-cam and less on the Boob Tube. Thanks!
Thanks for the video! I knew about diode switching, but I didn't understand how it could work for large voltages, such as in transmitters or various antenna switchers, not being aware of the "storage bucket/flywheel" characteristics of the PIN diodes. Cool, I have learned something new!
BTW, you have a really excellent drawing style - my computer drawn schematics and diagrams often don't look as good as your hand drawn ones!
Time to replace my noisy TX relay and filter relays with PIN diodes. Thank you for a great tutorial!
This was really helpful Alan. Thank you so much.
A fantastic video, as always. I feel like i really understand this now! Heading to eBay to grab some cheap PIN diodes and build some circuits to tinker with at 54mhz
Great video and great explanation. Never ever used PIN diode.
I did not know that about PIN diodes ..... very cool. I like the way you teach, just wish my old electronics teachers from the past could have done the same for me. .... I’m a slow learner.
We don't deserve you, at least I don't for sure. This is beautiful work. How I graduated and never saw a pin diode before, I'm not sure.
I have to say at first when I saw RF videos I was pretty disappointed (not really sure why), but lately I've been really enjoying them. Thanks!
Thanks from India!
Your videos are great!
Would have been interesting to apply a square wave to the control line of the pin diode to display pulsed transmission of a sinewave. Great range of video's well done. Joe G4PMY
strong in theory, practice and how to present thing simply... really great
PIN diodes are interesting devices. Another is an avalanche transistor. I once used the combination of both to create an extremely large and fast current spike. If I recall correctly it created a 60amp spike of a sub nano second length. It would be interesting to imagine a long wire antenna which could be 'tuned' by length with the PIN diodes also.
Thank you ! That was excellent. I think I now have at least some understanding of what I am looking at in the front end of my TS-930 schematic. ie. Switching of the bandpass filters. This video 'solved' it for me.
Very interesting, I was reading recently about how different I.F filters were switched using diodes in H.F receivers and I was puzzled about how that worked; am I right in supposing they employ a similar principle to what you describe here? Thanks for the informative videos!
Thank you for this. I now know that I understood little about how PIN diodes behave.
Does it gives high capacitance value if it be use as Varicap ? Because of high charges storage capabilities ?
Awesome video! It is so much easier when I can "see" what is happening to go along with the GREAT explanation. I was with you almost the whole way until I seen that it was still conducting even when it was reversed biased? I'll have to watch it a few more times I think. Thanks again for posting this I felt like a kid on Christmas morning lol I have a circuit in my head that I have been studying & trying to understand (for a very Long time) while follow along w/your video- Basically it uses a 555 timer to switch between 2 antenna's (using pin diodes) for Radio Direction Finding you might even be aware of it its called -Simple TDOA circuit w/a 555 IC? I really want to build this circuit but never have I just didn't have enough understanding on how it worked until now Great Job!
Yes - the PIN diode will conduct (for a short period of time) when reversed biased - this is due to the charge stored in the junction. Once the charge is all depleted or removed, then the device stops conducting. It is this stored reservoir of charge that makes the PIN diodes special, and geared towards switching RF signals.
***** I was expecting that they would stop conducting sooner (I thought the P-I junction held less of a charge or would dissipate it faster not sure why I thought that lol) until I watched your video & they didn't perform in the way I previously had thought Thanks
Excellent explanation sir. I have become your fan.
Excellent tutorial on PIN diodes. you're so good at explaining. THANK YOU.
Best video. Thank you. I need to do a presentation on these diodes for school. This really helped.
Glad to help! Let me know how your presentation goes.
Very good practical tutorial. thank you
I just started to learn about electronics, and like your video´s. What I don´t get in this video is why doesn´t the diode clip the negative half of the RF signal (when the diode is not DC biased) and pass through the positive half of the signal as it gets above 0.6 Volts. (that´s what I learned from the textbooks anyhow, maybe I should learn a bit more first before asking questions, but I´m curous).
Your videos are very well presented and are informative. You make an excellent teacher.Great job, Thanks for your presentations.
Thank you sir, this video helped with my PhD research.
great video thank you👍
Really nice... Well explained with both theory and practical ..Thank you for such a great lesson..
When the diode distorts the waveform on the negative cycle. what is the effect on "distortion" and/or the VSWR? Then what is the effect on the Harmonic component?
Hi Sir. How to use PIN DIODES as a power limiter to avoid damage from high level signals coming from the antenna? For example, when receive +6dBm from antenna, the diode limit this power to +3dBm to protect the LNA. How to calculate and choose the right diode for the desired limit value? Thanks!
Thanks for helping me prepare for my job interview!
I hope you get the job!
Thanks, clear, concise and paced perfectly.
Really good video. I've always been fuzzy about PIN diodes.
Thank you for the great video tutorial series! I have a question regarding TX/RX switching and ¼ wave transmission line. I have looked at various pin diode circuits for the VHF band and it appears that most circuits deal with the ¼ wave transmission line by adding 2 capacitors on each side of an inductor coil. I wanted to see if you could explain how to calculate the values to use?
You simple calculate the L and C values that have a Xl and Xc equal to the line impedance at the desired frequency. L =50/2piF and C=1/(2piF*50)
***** Thank you for the information.
n5xnq I think you'll like my newest video: th-cam.com/video/A1BAq0KxIdc/w-d-xo.html
Excellent Tutorial on pin diodes for rf switching. I always struggled to understand how the receiver front end did not get zapped, but the use of the 1/4 wavelength
of coaxial cable at the operating frequency and your explanation makes sense.
when the diodes are biased the rf passes through the pin diode to the antenna, but sees a very high impedence or open circuit at the resonant frequency.
I assume as long as the transmission is low in harmonics then the front end remains protected. Does the 1/4 have to take into consideration the velocity factor of the coax, or is it not as important?
sorry for the questions but I have always struggled understanding pin diodes in rf circuits your explanation switched a light on LOL thank you. Mark
Yes, you must take the velocity into account when figuring the 1/4 wavelength.
Very nice and more informative video, Thanks sir ! 😊😊😊
Very intersting video, i have made a diode switch before with a normal diode, but i was unaware that there were special diodes available that work much better. Where would such a diode switch be positioned in a RX/TX RF circuit? I take that if such a switch is used to switch between transmitting and receiving, would it be positioned to to turn on (pass the signal) when transmitting, or to turn on to pass a signal when receiving?
Wops, did not see the video entirerly, diregard my comment since it was already answered in the video!
A well done explanation - you teach perfectly, anticipating the questions that will surface during the presentation. I got a solid understanding from this video.
Curious if PIN diodes might be used for full break in T/R switch at HF frequencies. Guess this would be challenge to get 1/4 wave stub across all bands. Guessing the switching could happen based upon presence of RF - but perhaps not fast enough to switch in time to protect receiver? If made to work, could perhaps apply to 2m 70cm diplexer application?
They can be used, but would more likely be used to break the TX path much further up the chain, before TX signals are amplified much (such as at/before the modulator). Thus, they wouldn't be subject to blocking high-level signals. And, the 1/4 wavelength line trick wouldn't be used. I just thought that this trick was pretty cool (when doing single-band, low power applications).
*****
Thank you very much.
You note that PIN diodes can be used as variable attenuators at RF... however the scope presentation in your demo shows distortion (clipping) of waveform below baseline as you reduce bias sufficiently to attenuate. Any thoughts on this?
k1mgy In my demo, I was running with fairly low RF frequencies, where the negative half-cycle is long enough to "empty the bucket" of stored charge under low bias conditions. At higher RF frequencies where this isn't the case, then the change in RF resistance vs. bias can be exploited for applications such as variable attenuators, etc.
Can you make a video explaning how a Butler matrix beamforming network works, and how it could be used with synced SDRs for a DIY passiv radar system? like the kerberosSDR maybe with pin diodes?
Excellent video- I had a question, though- why is the forward bias current needed at all? If the positive half cycle forward biases the PIN, would that charge not get stored in the intrinsic region for use during the negative half cycle? Does the current need to maintain a positive average value?
To my understanding, it won't give you enough charge in the bucket to maintain conduction during the negative cycle.
@@w2aew Ok- I was thinking about it more, and maybe it has something to do with overcoming parasitic resistive losses. Thanks for the reply, and again for all your efforts in making these fantastic videos.
Great tutorial Alan as always!
Yet another fantastic video. Awesome explanation!
Would you have done a demo using the optical properties of a PIN diode....filling the bucket via photons?
Sorry, no demo on PIN photodiodes. Photons create carriers in the depletion region which quickly drift due to the electric field across the depletion region. PIN photodiodes are used typically in high speed applications because of the low capacitance.
Many thanks for the information. Very clear and concise.
Great video (as usual)... Thanks a lot for sharing your knowledge. Eric, France.
Very useful information and good style, thanks. I expected some kind of breadboard layout so the "custom" board surprised me. I can see the 50MHz signal would/could have been a problem for a BB. When do you have to go to a "custom" layout?
I'd say once you're dealing with frequencies above a few MHz it's a good idea to start getting off of the plug-in breadboard. My "custom" board is nothing more than a hunk of double sided copper clad, with some "traces" made with an exacto knife.