PLL's - The Voltage Controlled Oscillator (VCO)

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#115 This time I continue looking at another fundamental block used in a phase locked loop (or PLL), the voltage controlled oscillator, or VCO in short. I take a look at the 2 fundamental types commonly used - the relaxation and the harmonic oscillator and then inquire how the output frequency can be modified using an external voltage.
Datasheets:
www.ti.com/lit/ds/symlink/cd4...
Tested circuit schematics:
Harmonic oscillator: drive.google.com/file/d/1G3DJ...
Relaxation oscillator: drive.google.com/file/d/19J15...
More on PLL's:
Frequency multiplication: • PLL's - Signal Frequen...
FM demodulation: • PLL's - Demodulating F...
The Phase Detector: • PLL's - Digital phase ...
The VCO: • Video
References and further reading
- The Art of Electronics; Horowitz, Hill; Cambridge; Cap 13.13
Special Thanks to all my supporters on Patreon! Especially @afiskon and Ralf B.!
If you liked this video be sure to check out my other videos and you can also subscribe to be up to date with all the new ones!
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6 июн 2024

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Комментарии : 33

@MovieMationStudios 3 года назад

As a EE in University, I can say that you explain this stuff at perfect level that leaves me learning so much about analog design. Your content is pure gold man, thanks so much for making it!

@TeslaExplorer Год назад

He presents everything in full. I often wonder where this drive is in other enthusiasts! FesZ is beyond this.

@manoA98A 3 года назад

I really have to thank you. This is the best channel for LTSpice tutorial, you gave me a passion that I needed to find long time ago. I'm an engineering student in an Italian School and we don't do practice in our university, so you are really a life saver for me! My knowledge on ltspice is just thanks to you. I'm amazed by the fact that in 2021 you are still publishing new videos. You really are a wonderful person to share all your knowldege with us My deepest thanks, Mano

@FesZElectronics 3 года назад

Thank you for the kind words! I'm happy I can help your university experience! Why would it be strange that I still do videos in 2021? I mean LTspice is still a very common circuit simulator, even if its not the prettiest, it does a good job.

@KonradNineveh-nh6sm 8 месяцев назад

thank you for uploading these videos. Love ur content

@visnubobu9918 6 месяцев назад

Thanks love to see your every content

@sziluchannel Год назад

Best explanation of this topic on the whole Internet! Keep it up!

@sziluchannel Год назад

Could you build a circuit like the one you have explained in the begining of your demodulating FM signals video? Using the rf mixer and the local oscillator.

@PankajKumar-zr3tv 2 года назад

Love your videos man!

@custodiogomesbarcellos4972 3 года назад

Nice explanation!

@AUDIOETRADIOATUBES 3 года назад

great video again congrats

@Scrogan 3 года назад

Now I’ve never seen that kind of VCO before somehow! A sawtooth wave with a current mirror being controlled with a variable voltage. And the use of an H-bridge with it is neat too, but I can see why you decided not to use it. I think I’ll stick with using a vactrol and a Schmitt trigger + integrator as my modular synth VCO, the main reason being I can take he control voltage from my oscillator and feed it into identical vactrols to synchronise VCFs with my sounds. But if there’s a current-mirror based VCF design I may just swap over.

@creatingawareness1947 Год назад

Interesting video. How do you include pwm into the signal generated?

@alexengineering3754 3 года назад

Thanks for this video

@objection_your_honor 3 года назад

Will you consider doing a video on your AC variable power supply? Yours from another video looks DIY and I need one that's current limited like yours.

@odissey2 2 года назад

I believe that the Colpitts oscillator with varicaps is superior in terms of frequency stability and phase jitter, particularly at higher frequencies. Use of the relaxation oscillator is typically limited to the lower frequencies (

@mchabbi 3 года назад

In theory, a BJT can be used in a Colpitts oscillator, When constructed, the choice of BJT makes a lot of difference, and usually, the tank circuit is loaded by BJT and the oscillations die down when you vary the frequency (narrow tuning range). The sine wave is not as distortion-free also compared to a JFET if used as an active element. JFETs generate less distorted sine waves and are easier to work with when you actually build the oscillator.

@martijnklasing7815 Месяц назад

12:21 What would you do if you couldn't use the second voltage source connected to X3? In other words. How to control the current mirror from the voltage source conncted at V+?

@SaihoS1 3 года назад

Thank you for the lesson. The only thing left me in doubt. It is practically impossible to obtain a fill factor of exactly 50% with circuitry. There will always be some difference between the charge current and the discharge current. At the same time, you can be sure that the duty cycle will be exactly 50% if you divide the frequency by 2 using a trigger. Therefore, it would be very logical to use this prudently setting the VCO frequency to twice the required one and then divide it by 2. Isn't it?

@FesZElectronics 3 года назад

You are right, a perfect 50% duty cycle cannot be obtained by charge/discharge cycle since some of the charge gets lost because the capacitor isn't a perfect storage element. On the other hand, the H-bridge configuration used in the 4046 performs both the charge and discharge in every half cycle - the capacitor is never left at 0V but rather the Hbridge switches when the capacitor is either at Vcc or -Vcc, so any losses should occur in both cycles, giving the 50% duty in the end. I guess issues with the divide by 2 circuit will occur only at very high frequencies - modern day computers use clocks of ~4GHz; it much easier to make a 4GHz oscillator than an 8GHz one, I guess.

@rickbronx8528 6 месяцев назад

Hi, could you tell me what simulator you are using perhaps? I'd like to use it. Thanks

@FesZElectronics 6 месяцев назад

Hello! I use LTspice in all my videos

@mu8502 3 года назад

hey my friend I have a question: sometimes control voltage start from 8volt to 10volt(for example) but vco work with 0v to 3v(for example) volt what circuit can convert 8 to 0 and 9 to 1 10 to 3???????

@FesZElectronics 3 года назад

You could start with an 8V zenner in series with a resistor - its not perfect, but its simple - it will take the 8-10V to ~ 0-2V; otherwise, you would need an op-amp circuit to perform the subtraction (subtract 8v precisely) and then another op amp to multiply by 3/2 - this will make a proper conversion of the 8-10V to 0-3V.

@mu8502 3 года назад

@@FesZElectronicshi I tested it and subtractor was enough and my problem get done thanks you are best!!!

@mu8502 3 года назад

hey my friend how we can make an vco that be sensitive to microvolt changes example 3micro volt increase on control voltage ???????? I need to know this really!!!

@1900OP 3 года назад

The VCO may already be sensitive to mircovolt changes, how are you gonna measure such a low frequency drift if it's the case? You're also gonna need to take care of noise sources in the circuit that might swamp your control voltage

@mu8502 3 года назад

@@1900OP ..the main problem in my case is noises cause I'm using a timing circuit it's very important to reduse noise I can't reduse noises efficiently

@1900OP 3 года назад

@@mu8502 What have you tried? Decoupling capacitors and voltage regulators will do nicely. Also filters.

@mu8502 3 года назад

@@1900OP in 555 timer frequency and pulse width have changing(a little bit) ....I don't know why??? cause I'm using a pulse width to dc voltage converter or (pwm to voltage converter) a little change in pulse width or frequency can changes the dc voltage output maybe this not called as (noise)but it's like that....

@1900OP 3 года назад

@@mu8502 Got a schematic diagram of your circuit? Are you using a 9V battery?