Astable Multivibrator using BJT Explained
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- Опубликовано: 4 июл 2024
- In this video, the design of Astable Multivibrator using the transistor (BJT) is explained.
In this video, the operation (working) of the astable multivibrator circuit is explained in detail and in the end, the equation of the frequency of oscillation of the circuit is derived.
By watching this video, you will learn the following topics:
0:00 Introduction
0:27 What is Astable Multivibrator? (A brief introduction)
2:16 The operation (working) of the Astable Multivibrator when it is powered up.
4:44 The operation (working) of the Astable Multivibrator in the steady-state.
10:00 The derivation of Frequency of Oscillation of Astable Multivibrator.
What is Astable Multivibrator?
Astable multivibrator does not remain stable in any of the two states. And the output of the multivibrator continuously changes between the two states.
This type of multivibrator is used in the design of a relaxation oscillator.
In this video, the Astable Multivibrator is designed using the BJT and its working is explained in detail. And in the end, the expression of the frequency is derived.
The time period of the astable Multivibrator T = 0.693 (Rb1*C2 + Rb2*C2)
(Here the nomenclatures are used as per the video.
If the value of the resistor and capacitor is same for both transistor (Rb1 = Rb2 = R and C1 = C2 = C) then
T ≈ 1.4 RC
And frequency of oscillation f ≈ 0.72 / RC.
In this case, the duty cycle will be 50 percent.
The link for the other useful videos related to the topic:
1) What is Multivibrator?
• What is Multivibrator ...
2) Transistor As a Switch
• How to identify the Sa...
This video will be useful to everyone in understanding the working of the astable multivibrator when it is designed using the transistor.
#AstableMultivibrator
#AstableMultivibratorUsingBJT
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The timestamps for the different topics covered in the video:
0:27 What is Astable Multivibrator? (A brief introduction)
2:16 The operation (working) of the Astable Multivibrator when it is powered up.
4:44 The operation (working) of the Astable Multivibrator in the steady-state.
10:00 The derivation of Frequency of Oscillation of Astable Multivibrator.
For more Solved Examples on the BJT, check out this playlist:
ruclips.net/video/byPBZmCfsb8/видео.html
Thanks bro meri baat maankr upload krne ke liye
All the explanations of a two transistor astable multivibrator on RUclips, this is probably the very best one. Thank you very much Rushal Shah!
This is a masterful explanation! I admire you, Sir.
All the electrotechnician students from Brasil have many thanks for you.
Impressionante o quão bem vc explicou, muito obrigado.
Ll
P
Thanks sir, helped me a lot in my project explanation, keep up the good work.
This video time is 16 min 39 seconds but I have completed this video within 1 hours 29 miniutes 🤗🤗but concept is clear now ..thank you so much sir 🙌🤗❤️👍🙏
Incredible good explanation.
Great and simple presentation..superb
Thanks a Lot Sir, Hope you'll post more videos like these
Love From KUET,Bangladesh
You are a god among men. In all seriousness, you have helped me learn a lot about electronics. Thank you!
Thank you very much for the explanation
Good Graphics! I like the emphasis on how it works. Remember that the viewer is engaged in deep thought while you narrate so it might be a good idea to slow down the narration .
Now for a couple of questions. What happens if the resistances and capacitances are changed so as to “unbalance” the circuit. Also, can this two-way flip flop be extended so as to become a 3-way. Flip flop.
Further, it would be nice to see that circuit in action.
Sir, your videos are really helpful,that too me from a lower middle class background feeling your videos are really helpful, I would be pleased if u make some videos on JAVA PROGRAMMING
Thank you sir. Very thorough explanation from basics to calculations.
Thanks again
Very Helpful thanks
Thank you master.
Really helpfull,,
Thanks from indonesia
You subscribe a new channel called circuits analytica, this is explained in a better way. I learned from that channel....
great vid keep up the good work!
Very good explanation,👌👌👌👌
Nice explanation, thank you sir. Recently while searching in the RUclips, I came across a new channel - circuits analytica, only few videos, everything is nicely explained...
You are the best
Good explanation sir ❤️❤️❤️
Very good
explained well
Thank u very good explanation plz explain experimently on CRO also
Very helpful video sir. Thank you so much for your efforts. Can you please make a practical video also using cro for experimental purpose to measure T1 and T2
Thank you for the explanation. Could you provide an explanation video for the improvement circuit too?
Thanks sir ji 👍
Thank you again. Can you please include the improved circuit too? and also how do we improve the higher rise time? Is the square wave change due to low pass filter forming?
Wow uh r fantastic
BEST SIR
Thank you sar
Very nice
love Form Bangladesh
Please upload the video for improved astable multivibrator and emitter coupled astable multivibrator. It will be really helpful
Sir project is super... But if you add 2 led after r1 and r4. The idea would be It Much more clear by blinking leds.. Many thanks.. God bless you Sir
Thank you. One of the best explanations I've found so far. I have a question. I have an example of this with a kit. It uses polarised electrolytic capacitors. I didn't think you could swap the polarity, or charge it through the negative pin?
Please do make video on improved circuit 😊
Which book covers the topic as u explained i meant the total working of astable multi. I referred david a bell it does not have clear explanation of this??
This is a very good explanation. But there is still room to improve it. You are using expressions like Vcc - Vbe which forces each listener to IMAGINE what this means as an EXAMPLE number. If you change from Vcc and Vbe to typical values like Vcc 9V and Vbe 0,7V and also to the results of calculations like "the voltage will be - (Vcc - Vbe) to - (9V - 0,7V) = -8,3V minus 8.3V it will become more easy to understand. But wait! How can it be that the voltage between the base of the transistor can go below zero? compared to the emitter? My understanding is it goes down to (almost) zero which makes the transistor opening. But is does NOT go below zero (aka -8,3V minus 8,3V)
sir as soon as given the supply how does the capacitos is charging through that path as the capacitors are not connected to the ground
Can you provide proving circuit which you talked about in the end of the video?
Sir please explain about the voltage across base of transistors
Nice Explanation. SIr, I have a Circuit , similar to astable multivibrator. It has been implemented using a NPN and PNP transistor . Base one one transistor is connected to collector of other transistor. I am unable to understand its working.
If I use Capacitor Polarized, operation of the circuit will not be affected because 0.7V < the Max Voltage Reverse of the polarized, is this true? Thanks Bro!
Good day, I just did this cct but it doesnt seem to work. What is the minimum duty cycle it can deliver. I wanted a duty cycle of 16% I want to know if it can deliver that. Thank you
Is there any examples with the help of detail explanation for this concept ? If there , please let me know.
Thanks a lot for this.
Does this mean polarised capacitors are a No No
Sir,How the waveforms look like at VB1 and VB2?
At starting point u said that Q1 is short circuited so how it will be forward biased and i need current direction explicitly so kindly reply pls
You painted the rose line (current), that goes THROUGH the left capacitor. How can it be, if capacitors do not conduct electricity?
Mst
how capacitor will chrage in dc voltage
🙏
As soon as you apply voltage, the caps don't charge instantly. It is a short circuit as they say. This means both LEDs must turn on, maybe one before the other. Otherwise the system will fail.
If both transistor are different ( like one is npn & other is pnp ) or not identical, then what happens in the practical o/p waveform of astable multivibrator?
one will not conduct as current direction are vaired
Hello there, may I ask how do you make your videos? Those figures I mean.
Pen Tablet
how we will set the values of resistance and capacitor of the multivibrator any derivation?
At 10:00, I have already provided a derivation. Please go through it.
How does the transistor turn on for the first time?Because as soon as we give vcc then both the capacitor start charging through Rc1 and Rc2 path,as a result both the base should be negative.
In reality, both transistors are not same and there characteristics are slightly different. So, when we trun on the transistors then one of them will get turned on first and it will prevent other on from turning on. In the beginning, I have explained that.
I hope, it will clear your doubt.
How did u take those current directions through capacitor
The current is flowing from higher to a lower voltage. (Vcc to the ground). When the transistor is ON, it acts as a switch and offers minimum resistance. So, the current will flow through the minimum resistance path.
I have already shown the direction of the current through the capacitors.
You refer a channel called circuits analytica, explained very well...
But why lets say Q2 is not constantly on by the current provided to the base through Rb2? Why the current through Rb2 is completely absorbed by C1????
You talked only about the charging of the capacitors, does not they get discharged?? What is the effect of discharging??
The voltage across the capacitor changes between Vbe and -Vcc + Vbe. The direction of the charging is getting reversed in between.
Great Presentation.
I want to know about a similar circuit . Can you please share details , how we can implement , this type of circuit using NPN and PNP transistor?
Why the current direction is changes from the path Rc1 to Rb2
Because now Q2 is OFF, it will act as an open circuit and provides very high resistance. So, the capacitor won't charge through Rc1 and Q2. Also, Q1 acts as short in the ON condition. So, the capacitor will charge through Rb2 and Q1.
I hope it will clear your doubt.
@@ALLABOUTELECTRONICS thanks for quick reply sir ❤️❤️
@@ALLABOUTELECTRONICS Thanks sir, it helped me too :)
👍👍👍🌹🌹🌹
I cant quite understand how its possible to charge a electrolytic capacitor from the negative site? Also, why isn't both transistors ON while there is Vcc on both Bases of the Q1 & Q2 through RB1 and RB2
Of course electrolytic capacitors won't work. Ceramic would do the job. The reason both transistor won't be ON is, both transistors are not identical. There will be a little mismatch between them. So, initially one will conduct more than other and eventually in the ON condition. I hope it will clear your doubt.
@@ALLABOUTELECTRONICS but the base of every transistor is connected with the Vcc via a resistor
@@MFDOOMgr Yes, thats true. But as I said, due to mismatch, only one transistor will go into the saturaiton and it will prevent other from going into the saturaiton.
I have seen these circuits working with electrolytic capacitors. I think that in this video is not quite correct to say that the capacitor is being charged through the RB resistors, it is instead discharging through those but since the voltage when that happens is negative as it discharges it becomes more and more positive until it eventually crosses the 0 Volts limit and then becomes positive up to 0.7 V which is enough to trigger the base of the opposite transistor.
Difference between Schmitt trigger and a stable Multi vibrator
In the Schmitt trigger, the output changes based on the input signal. Depending on the input, the output could be +Vsat or -Vsat. But in the case of the astable multivibrator, the output continuously changes between the two states.
Can anyone tell why Capacitor C1 reverse charges , as Rc value is less then Rb , it should be reverse of what is said in the video... Ref:- 5:01
when Q1 is ON, the collector terminal of the Q1 is at ground potential. (In ideal condition). Therefore, the one end of C1 which is also connected to Rc is at ground potential. And therefore, the capacitor will not charge through Rc. But rather, the current through the capacitor will flow through Rb. Therefore, there will be change in the polarity of the capacitor voltage. Or in other words, the capacitor will charge in the reverse direction. I hope, it will clear your doubt.
@@ALLABOUTELECTRONICS Got it. Thank you..
It is not too bad, The English language is not spoken so smoothly but in spasms, A waveform diagram showing the collector and the base voltages synchronised together would have been more helpful. They would have sown the real time diagram and not the symbolic circuit. The diagram shown in this video is never attained as a real circuit but as an illusion of the real circuit. The graphical diagram of the timings and waveform are closer to reality than the spoken or the written language and also the circuit diagram. This is an old fashioned manner of teaches not any different from my teaching 70 years ago. Yes I am a very old man. Computers can be made to show the dynamics that our blackboards could not, A waveform diagram with its dynamics would have been a better modern proposition,
Sir can u tell me the best book to learn electronics
There are many books. But for basics, you can refer principle of electronics by Malvino and electronic devices and circuit theory by Robert Boylestad
Thank u sir
@@ALLABOUTELECTRONICS sir i have a small doubt
In an astable multi vibrator using transistors if i removed collector resistors and replace with LEDs what would happen?
sir provide us all content in pdf form
mono, bi stable???
They will be covered very soon. (using BJT). Using 555 timer and op-amp, it is already covered on the channel.
👌🏻👌🏻
Hinglish me padhaya karo yarr
when yu hear indian yu know its legit
I am india, you are from which country?
Kind of confusing
Awful music
Useless because they canna no speka Englis
not too good explanation...
Only theory... Oh god... Pls explain with a practical circuit... Be. Practical man...