#38: LC tank circuits and the Colpitts oscillator

[@Guardboy62]

Well done! This is the best information I've found online. I'm reviewing after over 10 years out of the game and this was full of 'light-bulb' moments. Thanks! :)

[@brianfitzgerald6142]

Thanks for this very clear description of the Colpitts! I really appreciate your inclusion of the mathematical principals behind its operation.

[@midnightman011]

More oscillators! .. you get the most views for those anyway .. that was a good explanation of the Colpitts .. thanks for the hard work posting videos on youtube

[@omaruhh]

Thank you! I finally feel better about learning this subject. This has been a real struggle for me until now. Thank you.

[@josezilio]

Oscillators are no longer a mystery after seeing this video. Thank you for opening my mind.

[@coenraadmulder]

Great presentation, going through the math, then a build and measurement demonstration, very well presented.

[@TheRadiogeek]

I enjoyed this video very much. You did a great job explaining the oscillators and showing how all the parts Work together. Thanks.

[@jxxcc]

Excellent historical, theoretical and practical explanation!

[@agstechnicalsupport]

Clear and to the point ! Colpitts and Hartley well distinguished. Thank you !

[@vimeel4420]

This is the best video about oscillators. Thanks!

[@sadunnakipoglu9471]

Thank you and appreciate your effort. Greetings to you from Turkey .

[@SumNumber]

Very clear explanation . That circuit worked very well in amplification and looked very pure . Cool stuff man ! :O) ( vfo)

[@luisbosch9433]

Thanks for a good “chalk board” presentation. Be nice if you could shown historical examples with tube circuits.

[@kolinevans9127]

thank you greatly for making this video - it helped me understand the simplified gredation of this layout - i already understand the basic 'math' however there is a lot of 'alledged' based on what excatly is occuring - so thanks - as you have simplified it and it works.

[@koenvandemoortel2206]

Interesting and nicely explained, but I tried it with a BC548C and a 9V battery, and some bigger capacitors to get a lower frequency, but it didn't do anything. Only with a bigger inductance (10mH), it started after I "shorted" the 1M resistor with my fingers. The frequency was pretty stable, but it was a very "deformed" sine wave. Are there any rules to observe here?

[@roberttso1079]

For the Hartley, are the dots on the inductors correct?

[@jonasdaverio9369]

Nice video. One question: why is it stable? Usually with oscillator, you'll have to have non-linear element so that the loop gain is exactly 1 (if it's just slightly more the oscillation will go out of control). I often saw light bulbs or PTCs. What is the equivalent element here? I guess it must be the non linrarity of the transistor. How does that translate in distortion?

[@kamleshchavan7451]

Brilliant explanation sir. Sir I would like to ask you, you have any video explaining in detail every section and components used in RF transmitter receiver module circuit diagram

[@leonardorodriguez4152]

Hi, this is a very instructional video. I am looking forward to setting up a DC Tank circuit with both the inductor and the capacitor connected in parallel, where a battery could charge up the capacitor, and after the battery is removed from the circuit, I would like to show relatively "undamped” amplitude oscillations on one oscilloscope screen. I am not sure if the antenna or the transformer that you refer to in this clip are critical to the purpose of my circuit. In order to design this type of circuit, could you please share with me appropriate capacitance and inductance values, the type of capacitor, battery and oscilloscope settings? Thanks for your attention to my request!

[@divtec1]

Very articulate explanation.

[@stephenuy9812]

very easy to understand explanations. good job!

[@singhonlo67]

The capacitance and impedance of both the probe and coaxial cable would load down and detune the oscillator? The stray capacitance of the breadboard jumper wires would only decrease and not increase the natural frequency?

[@amresheternalphysics]

Very informative and real video, please tell me how can a fm transmitter radio be made using LC clapp oscillator with a single transistor.

[@dangryder6050]

Sir, for homemade eddy current inductor proximity switch should I prefer an op amp or transistor Colpitts?

[@Infinitesap]

Could you make some videos about the differential equations? Especially the second order thing.

[@rodolfoescobar3108]

I can't make that circuit work for other frequencies. How can I design a suited amplifier for an arbitrary freq? I know that I need a Av >= 10 but the design it's harder than I thought when you take the loop into account.

[@Yureka-ox5jn]

Can you draw graph on x and Y scale for the signal at output and at both capacitor? this would give more insight about how is current and voltage changing with respect to time

[@shahzebnoor1683]

Bundle of thanks Sir. But I have a question about the two capacitors how the circiut oscillate . i think the inductor charge through C1 in first +ve half cycle which also create a +ve half cycle voltage at base of transistor and after that inductor discharge through C2 which create another -ve half at the base of transistor and again same cycle repeat. But frequency is constant the inductor should make resonance with one capacitor only. Help me on this Sir

[@Alejandro-qf9ij]

Can you reach the high GHz frequency?

[@sohammajumder9010]

I need to understand how the feedback is creating the effect of oscillation. That part was skimmed through. Kindly point me to a video that can describe mathematically (maybe via KVL) or intuitively what is happening during feedback.

[@bourhandernayka400]

Hello, what did you rely on while choosing the values of the resistors you used? And is that a 1MegaOhm resistor? (it’s not clear) And are such small capacitors (1nF and 10nF) able to produce and sustain such high frequencies?

[@902Steeler]

Nice video. I built a colpitts and fed it into the collector as oposed to in the base bias. I used a tunable coil. My I could tune between 400 and 800 KHz. We are building breadboard am transmitters in school. Maybe I will make a video

[@marcdraco2189]

Math went woosh - theory hit me right in the brain! Great teaching.

[@oceanblues_arg]

Hi, I'm using Google Translate because my english is not good. How did you calculate the value of the 0,001uF Output Capacitor? Thank you

[@chandanjanardan3102]

can you show the calculation of how value of resistance is taken. and can it made by using jfet?

[@irgski]

The scope probe adds impedance to the circuit so the measured frequency does not equal the calculated frequency.

[@madtscientist8853]

1. Instead of having a spark app. You want to pulse with modulator. 2. You want 2 coils, one capacitor With as close as you can the same values. 3. You want One coil clockwise the other counterclockwise. 4. And you want the entire circuit in series never parallel. 5. From there, you just want to test out. Where on the circuit you put the ground. You'd be surprised that different voltages you'd get. At 1.5V I have gotten 10 -20v But that's if you know where to put the ground on the circuit.

[@Alejandro-qf9ij]

what is the maximum frequency that can be generated with this circuit

[@grzesiek1x]

so actually without transistors I can't make the oscillator? I mean everywhere is shown only the tank the inductor and a capacitor but with those two I can't make them to oscillate (maybe I miss something ). I have already maden a similar circuit with a quartz 4 MHz and I get a beatiful (almost) a sine wave with 4.00 - 3.99 MHz but when I experiment with only capacitor and a inductor coil I makes only a short circuit and on my oscilloscope I see nothing (almsot a straight line like a battery, nothing special, experimented with different coils and capacitors and always I get the same result - nothing :/ )

[@anshulgangwar8025]

Can we make it with help of mutual induction I think Hartley oscillator is much easier to understand

[@anwaralfawdaei3381]

amazing explanation. keep on

[@zzaamm4236]

How to build circuit using ic function generator to obtain 100k HZ and 15 v output ?

[@charafmohammed6646]

this is the top video, thinks for information brother

[@brothercavil491]

If the node between the two capacitors is AC ground, why doesn't the AC current from the output just get dumped into ground? i.e. if ground is between the caps, how does that ensure that as one charges up, the other charges as well?

[@brothercavil491]

For anyone with the same question, I found my answer: the LC tank acts as an open circuit at resonance, so there's no AC current entering the tank from Vout; there *is* current flowing in the tank, but it's just being passed from caps to inductors and back. This current flows the same direction thru both caps, creating voltage drops in the same direction, but the ground reference between them means one is a drop from positive Vout to ground while the other is from ground to -Vout.

[@alalv8617]

This explanation is something that it is always missing in all videos. Good for you that you have written the answer. That's also why the two capacitors are considered to be in series, not evident by just looking at the scheme.

[@___xyz___]

I realise this may come off as a very naive thing to say, especially for someone who is very good at understanding circuits theoretically, but can't educators just provide a schematic with a simple breadboard configuration at the very beginning of a lesson so that us not-so-smart-right-out-of-the-box people can follow? Often times with highly technical video lessons, I find that I might not be able to finish, learn properly their contents and correctly reproduce the results, until I have at it again. The times when I learn the most and gather the most insight are when I immediately set the circuit up experimentally, and produce myself questions about the observations that I make. Even after having given up on a lesson, I may work on the circuit and eventually realise where I was confused. Then I could catch up with the lesson and have my questions answered. Hands-on circuits really do the trick. Just a suggestion...

[@___xyz___]

Please don't misunderstand. This is a great video and you do a wonderful job as ever explaining the proper uses of oscillators! It was not meant as an insult by any means even though it sounds disparaging! Thank you ever so much!

[@radiophysicsandelectronics6923]

Thanks for your comment and rest assured it does not come off as disparaging! You make an important point about learning styles and assumptions of people offering demonstrations and explanations. I'll think about how to incorporate your comments in some future videos -- providing the demo first, showing exactly how it's done, and then offering the theory behind it.

[@omundofisica9785]

Very good!

[@tn7707]

The Best lecture

[@elektronikdevretasarimi4005]

I thing Theres is mistake about base biasing?

[@elektronikdevretasarimi4005]

I beg your pardon.I am mistake.You are right.I am sory

[@InterdimensionalWiz]

superb thank you.

[@markderlo212]

How does it perform when you change the voltage supply ? how many % does the freq change with say 10%,20% Vcc change? Is the freq stable when you change the transitors to have different hFE?

[@tugaric]

You have no capacitor at the input of your emitter follower amplifier... there is dc current in your tank circuit ... is that suppose to be that way? o.O Also you wrote 1mili Ohm at your RB resistance i m guessing it sould be Megaohm

[@maxtech2702]

Can c1 and c2 be the same?

[@brothercavil491]

C1 and C2 act as a voltage divider so as to attenuate the amplified output- you want gain to be 1 so that the positive feedback doesn't create oscillations that grow without bound. If that happened, you'd probably get a square wave instead of a sinusoid as the output would keep hitting the rails.

[@mdesm2005]

funny how the current keeps going in the same direction once the capacitor runs out of charge , this is cause by the collapsing mag field, ok, but the voltage is flip around. How can the voltage between the cap//inductor flip but not the current direction? Even for that brief period in the cycle.

[@meowman8958]

This is due to the fact that inductors try to resist any CHANGE in current. This is important because when the capacitor finally balances it's charges (aka completely discharged/neutralized), there will no longer be any electric potential from the capacitor. This will mean that current should drop. But our inductor does not want that to happen! So it continues the current in the same direction as it was going before. Now this is very important. This direction of current when the capacitor was inducing it's own potential can be seen as negatively charging the positive plate of the capacitor. When the capacitor's potential is gone, the inductor will continue the current in that direction, which will cause the formerly positive plate to become negative, and vice versa for the other plate.

[@dipeshpatil666]

loved it

[@hanskassier5048]

Brilliant

[@intheshell35ify]

Sounds like the drone bot workshop dude.

[@XPFTP]

funny people think spark gap is no longer out there.. but it is everyday probley in the 1000s range.... welders ..... spark gap ...

[@ThePaulbilek]

Nice explanation of circuit. The theory, well it's theory, too long.

[@tryhard2451]

The audio isn't great man please work on it

[@wiccatubitube]

bro you explained everything but oscillators..not satisfied...eyewash video..wasted my time.

[@mejiqal]

he dosent know what he speak and dosent know how this work..nothing explanied in this video beside the fancy math to look smart, yet math its only a way to see a expiramnet in different way and not the other way....what more scary * that people understood what he explanied, but he didnt explain nothing and the right question if you ask him you tackle his mind, mean like a computer that stuck and realise that he dosent understand how it work