Added: 3 years ago
From: AllAmericanFiveRadio
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  • Thanks for the very elegant demo on the basics of biasing and amplification. I tried this experiment using basically your set up. I could not get a clean signal (severe clipping) for any of the R2 & R3 settings (through the full range) at the collector.

    I have two questions. Does the beta of the transistor matter for your set up? Also if my signal input level matters in getting a clean output. I had a 1.2v rms sign wave at 1000 HZ as the input signal. Appreciate your response. Thx

  • Thanks rschandran

    Yes the beta does matter. The higher the beta, the higher the gain of the transistor. So a high beta transistor can be easier to over drive by the input signal. Everything is important in the circuit. I think the best/fastest way to learn is to study existing circuits of the type you want to build. A lot of time and experimenting has gone into a successfully executed circuit.

  • Great video. And as someone mentioned earlier, very pleasant to listen to and easy to follow, thumbs up from me

  • You explain things in such a smooth, calm, easy way that it's understandable, thanks!

  • Thanks Mrluke1308

  • Thanks cumesoftware

  • Hello i really like your video

    You explain verry well

    Can you make one video for the 555 timer

    cause all the tutorial on the internet not explain well like you

  • Thanks myworldismine72

    I'll put the 555 timer on my YouTube todo list.

  • Thanks for the terrific video - very informative! I do, however have one question; what is the purpose of the R1/C1 combination? I remember you mentioned that they act as a positive voltage supply, but why is this necessary?

  • @flurng

    R1 produces a voltage drop for the emitter which produces a bias voltage for the base. C1 stabilizes this voltage. Without C1 the bias voltage will change more when current flows through E and C of the transistor. The more the bias voltage changes, the more the the current flow is influenced by the current through the transistor changing the characteristics of the amplifier.

  • jees i want a oscilloscope but they're so expensive

  • @wow1022

    Flea markets and Ham Fests are a good place to look for a used one. Good Luck!

  • how is the collector the OUTPUT? seems like it would be the EMITTER as the output, because it is combining both voltage from the base and collector.

    (not criticizing, just new to transistors and would like to understand their use in audio amps better. Thanks.

  • Thanks submission123456

    It can be! It depends on your purpose for the circuit. Here are the three popular configurations. Common collector (this video), common emitter, and common base amplifiers. Just Google them and you will get lots of information. Also look for my video on Navy Electronic training. The link to the downloads is in the description of the video. 24 volumes, PDF files.

  • @AllAmericanFiveRadio

    wow, thanks alot, the videos are great!

  • Thanks submission123456

  • nice work!

  • Thanks sloppyoscar

  • Is it possible to run the transistor circuit with dual supply?

  • @marsenification

    Yes but usually a common ground is needed between power supplies.

  • @AllAmericanFiveRadio Thanks, for your answer. I new to electronics but I want to built transistor amplifier, so the amplified signal have 0v as center swing (As far I know this is related to Voltage reference). There is many explanation on the web to do that by using op-amp. But no explanation to do that with transistor. Can you tell me what needs to be changed in single supply transistor circuit to run on dual supply? Thanks before.

  • @AllAmericanFiveRadio Thanks, for your answer. I new to electronics but I want to built transistor amplifier, so the amplified signal have 0v as center swing (As far I know this is related to Voltage reference). There is many explanation on the web to do that by using op-amp. But no explanation to do that with transistor. Can you tell me what needs to be changed in single supply transistor circuit to run on dual supply? Thanks before.

  • @marsenification

    I'm not sure how you wanted to use your dual supply. I would need to know what are the voltages of the power supply. If you can get from 6 to 9 VDC out of it, that is all you need for most transistor circuits.

  • @AllAmericanFiveRadio the voltage are +9v and -9v with a common ground. I want to use dual supply because difference output characteristic of the amplified signal. A bit of topic, as far I know, in op amp application, if we use single supply (positive supply), the amplified signal cannot swing below 0v (ground), the amplified signal only swing in the positive region and the center swing is usually called virtual ground (V ref). Any further reading for this problem on transistor basis?

  • @marsenification

    Well, you could use just the common ground and the Plus 9 VDC or just the common ground and the Negative 9 VDC. If you want to make a power output audio amp you could use it as 18VDC and just forget about the common ground from the power supply. If you want positive 18VDC use the negative 9VDC as ground in the circuit. If you want negative 18VDC use the positive 9VDC as ground in the circuit.

  • I am new to electronics and my question is why you have a capacitor C2 on the base lane?

  • @miyukiTS

    C2 blocks the DC from the circuit in front this one or from a signal source, and only lets the AC signal through to the base to be amplified. If a DC signal was allowed through, it would mess-up the basing of the base of this transistor.

  • This is explained very well, thank you. these are awesome lab examples for beginners. 

  • Thanks gecogexx

    I have a few videos for beginners. If you have any ideas let me know.

  • I thought biasing meant the current from the emitter is half the supply voltage

  • @PhuckHue2

    It depends on the purpose circuit.

  • @jinnaraka

    Download the Electronic Navy Training 24 volume courses. Find my video and in the description is the download link.

  • Hey AllAmericanFiveRadio: I have a fairly basic circuit  I recently attempted to build and I fried the microchip el75715 which is a Pulse width mudulator chip. I bought the resistor and caps to build it and destroyed the microchip. To make a long story short I would like to hire you to put this little circuit together. I would paste the chip's page but Youtube won't let me. Google el7515 intersil then visit page to click on circuit pdf file.

  • Hey AllAmericanFiveRadio: I have a fairly basic circuit I recently attempted to build and I fried the microchip el75715 which is a Pulse width mudulator chip. I bought the resistor and caps to build it and destroyed the microchip. To make a long story short I would like to hire you to put this little circuit together. I can send you the pdf page link if your interested.

  • Great video! thanks.

    What I didn't get though is how to figure out what voltage is the correct for biasing.

    I mean, why you chose 6V and not 4V?

    According to oscilloscope the sinewave looked identical..

  • Thanks warpie

    It depends on the transistor mostly and also what the circuit is going to do. The best way to start learning is to study engineered circuit that you are interested in.

  • Great vid, what would I do if I wanted a pulse dc instead of a signwave? Whats making the signwave anyway when a dc is connected? I'm guessing the r1 c1 tank is inducing a signwave?

  • Thanks donotfret,

    I used a sine wave generator for this demo. The same generator can produce square wave also. Most YouTubers are interested in audio equipment so that's why the sine wave. The transistor is making the sine wave at the output. At the output the transistor varies it's resistance which causes the DC to vary. I used a sine wave at the input so it varies the DC as a sine wave at the output.

  • @AllAmericanFiveRadio

    Thanks for the info. Funny thing though, the dc should be only dc ripple if indeed the base simply causes a resistance fluctuation regardless of if base is signwave..... because after all the power source is only dc. Perhaps the nonlinear characteristics of the transistor has something to do with it? Is that correct? I'm asking this question because I'm looking for a dc ripple source for a project on building.

  • @donotfret Class A bias is linear.

  • @AllAmericanFiveRadio great, I'll check out the class a oscillators. TY

  • What was the voltage of the input signal? And when biasing, should I bias it to where the voltage divided by the resistors is equal to the input signal to get a strong enough amplification without it clipping?

  • Don’t remember the voltage of the input signal, it saw small, less than a volt. For class A you bias the tube/transistor so that the input signal can swing the output equally between the top and the bottom of the power source for the output.

  • @AllAmericanFiveRadio Thank you, that clears things up.

  • Thank you Sir.

  • please see my videos and tell me where im wrong and what should i do????

  • Thanks. very usefull information as i am working on discrete jfet based preamplifier and finding i wide range of variables in the charcteristics of jfets. This gives me some good techniques for biasing - instead of all the crazy math:) Now all I have to do is buy an osciloscope-ouch:)

  • Well math is good if you know all the variables, which can be problematic. Everyone I know that designs electronics uses oscilloscopes. They are extremely useful if not indispensable. Thanks.

  • and if i just add a tank circuit in base of the transistor and bias it with collector along with resistor and add a feed back coil to collector...will i make a radio????

  • More likely a transmitter. YouTube search "Build FM One Transistor Transmitter MOD Project 3-3"

  • please help me make a simple transistor radio not a transmitter...i dont have ic like MK484 or ZN???..i have NPN 2n3904 please tell how can i make a simple radio with that??

  • but which transistor you are using i mean its SerialNo??? the resistors are set to a specific NPN transistor..14k and 34k resistors are ideal for which NPN transistor please tell the serial...

  • The NPN transistor is from a Radio Shack Pack of general purpose transistors.

  • Awesome job!! Thanks for sharing, it helped me a lot!!!

  • Thanks! Glad it helped.

  • Ok, I think I get the point; what really matters, is the current flow - not the voltage alone. If the current flow is limited to safe level, virtually any voltage can be applied at the base. On the other hand, I guess that even a low voltage, say 1 V, could destroy the transistor without any current flow limiting at all. Thanks...

  • Ok, but I still don't understand how the NPN can survive the 12 V on the base...

  • This is done most often in switching circuits. The major current flow in this circuit is through E to C. When the base becomes positive enough the transistor goes into saturation which is the highest current flow possible for this circuit. The current flow through the base is still small. Go down to Radio Shack and buy some 10 cent transistors and experiment. That is how you really learn.

  • I really enjoy your videos - this one is noe exception! Howerver, here's a few things I am wondering about: 1) How come you can apply almost 12 V on the base without destroying the transistor. I thought even 1 V would be too much? 2) What is the purpose of the input capacitor C2? 3) What is the purpose of R1 in parallel with C1? Thanks!

  • R4 is the load/current limiting resistor. Without it the transistor would burn out. If you build this circuit you will get the same results, I used no magic. C2 blocks DC but lets the AC signal through. R1 & C1 are for biasing, together they act like a battery.

  • Still very complex for me to understand, but it was a very good video, Thank You.

  • I didnt get it fully, but thank you very much.

  • it is very clear!! you explain better than my teacher. damn he talks so fast..

  • Thanks!

  • Well done. Your video is easy to follow.

  • Thanks!

  • thanx, thanx, thanx........................!

  • You are welcome. I have a free ebook you may like. I will login as tubeshortwaveradio and leave the information on your profile. Thanks.

  • 5 stars, excellent tutorial!

  • Thanks.

  • aaaa i dont get it!!!!! :(

  • Then you're qualified to be a Nortel Networks Executive.

  • hahahahaha, transistors are my weakness

  • They are very interesting. I uploaded the Navy Electronic Courses to my server. There are 24 PDF volumes and they are excellent. I did a video on the Navy Courses and the link to the download URL is in the 'more info' of the video. I think you would like it. It is great information.

  • Very well explained thank you great job!

    This will help me develop more amp projects.

  • That's great! And thanks.

  • Thanks! I liked your clear explanation why the clipping occurs when you lowered the biasing resistance in R3.

  • Clipping occurs here because the circuit tries to put out more, Neg or Pos or Both, than the power supply can deliver.

  • Thank you for a lucid presentation

  • I had been looking for the purpose of that pesky r2 for a while now, you helped immensely! I am looking to build a 2 tube amp in as simple a manner as possible (3 res and 2 coup caps) and this really helped me understand the usage of each resistor! thanks!

  • THANKS!

  • Excellent show, thank you. As far as I noticed on the oscilloscope as you decreased the resistance of R3, before the transistor got into complete saturation and signal disappeared there was some clipping in its amplitude. Does it sound as nonlinear/unlinear distortion? That explains what happens with the signal when resistors drift off their values. I would really appreciate if you uploaded some videos with IC amplifiers as well. Thanks a million.

  • The linearity usually determines how fast the volume/signal increases and decreases. If there is distortion and it is not due to the input sign being distorted it can only be clipping at the top or bottom or both. Thanks.

  • I have no real knowledge of electronics (actually, I'm yet to become a beginner :)), but despite that, all the concepts you're describing here appear so simple and easy to understand. As joernone said, a real legacy! Thank you very much for the education you provide.

  • I have read a number of books and if you could understand them, you did not really need to read them, so Im not sure what the point was. I like getting to the point. Most everything in electronics developed from experimentation first, then came the measuring and then the math. Math help to predict result and is an important starting point.

  • I have worked in many electronic labs each costing millions of dollars. Companies would not spend this money if experimentation and testing was not absolutely necessary. THANKS!

  • Awesome video, You're one of the few people on YouTube that actually educate.... keep up the great work and very much appreciate your videos.

    Take Care,

    Dave

  • Thanks very much Dave.

  • Rick,

    Probably the greatest benefit of your vids is that they'll digitally remain here for a very long time to come, long after we current viewers are gone. I'd say you're generating a pretty solid and worthwhile legacy.

    As usual, great job, my friend.

    Regards,

    John

  • Thanks John.

  • Very good explanation. How are the values of the resistors determined without this setup? This looks a bit different from a triode circuit because of the 2 bias resistors to the base.

  • The easiest way is to look at other circuits. The trend for biasing is higher resistance in the front end and lesser resistance toward/at the speaker, in audio amplifiers. This setup did have a good range of resistances for R2 and R3, that would still produce a good output, did not get to show because of time. Tubes usually dont have R3 resistors in the circuits because the internal elements of the tubes supplies it.

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