Transistor Base Bias Circuits - Finding The DC Load Line & The Q Point Values 

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"The Organic Chemistry Tutor"... Kind of a trademark name for a chemist handling physics so exceptionally! Thanks a lot for all these years... Please never stop.

Can't count how many times this channel has helped me out

This is the clearest explanation of DC load line I've heard!!! Great content!!! THANK YOU!

I’d be happy if my semiconductors professor was a tenth as good as you at explaining this stuff. Excellent video!

Great tutorial in physics by a chemist! Who knew that you can top them all?! Thank you for the detailed explanation. Your great effort is much appreciated on this critically important and versatile component.

I have watched so many videos on q point but this one i can perfectly understand.

Very nice explained, I have Q-Point in my pocket now!

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Very well done - to the point, well described and easy to follow!

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I really hope you can make a series of tutorials about the AC circuit . thank you so much for helpful content

Excellent video - a clear explanation on BJT biasing circuits.

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great to learn or relearn video.... nice to re-see this q-point info before making an arduino circuit... thanks a lot...:)

This is quite helpful. Thank you very much!

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Beautifully explained. I find myself rewatching and reannotating your videos, lol. Taking more notes in case I missed anything. One question I have is, how is this applied to amplifiers? Can I just use this method and plug my guitar or a line-level signal into the base and expect an optimal amp or is there way more to it?

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Did not have much knowledge about transistor, but this video enlightens me much. Great job!

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Can we use the information on the datasheet to design an amplifier?

In the analysis of circuits that make use of resistors, diodes and transistors, it is necessary to determine the operating point (voltage and current) of the device connected in a network, which is made from devices whose parameters are known. It is often necessary to determine voltages between terminals of a network with no current flowing. Consider for example the network which consists of two resistors R1 (terminals marked A and B) and R2 (terminals marked C and D). Their ends (A and D) are connected to the positive and negative terminals respectively of a power supply of 12 V dc. The other ends of the resistors are left unconnected. Suppose that the resistors R1 and R2 are 10 ohms each. What will a voltmeter read if it is connected between terminals A and B? What will be the reading of a voltmeter connected between the terminals C and D ? What will be the reading of a voltmeter connected between the terminals B and C ? Electrostatics and circuits belong to one science not two. To learn the operation of circuits, Current and the conduction process, resistors, capacitors and inductors and how discussing these topics with a unified approach makes it easier to understand how there is a voltage of a single wire connected to one terminal of a battery watch these two videos i. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-TTtt28b1dYo.html and ii. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-8BQM_xw2Rfo.html The last frame References in video #1 lists two textbook 4 includes topics that discuss simple networks and the physical processes which causes the appearance of potential drops. Specifically, in Chapter 3 discussions of load line graphs both dc and ac and their use in fixing the operating points of devices such as resistors, diodes and transistors are included. We continue for now with a brief discussion of the cause of the voltages between the dofferent terminals of the network example in this post. When the network is made, electrons will enter the battery positive terminal and the potential of the resistor R1 would have been raised. The battery positive terminal, would drop in potential due to the neutralising action of the few electrons, but then its chemical action will quickly restore its potential difference (p.d.) to 12 volts. The migration of electrons will stop, when the potential of the resistor equals the battery positive potential. And all this happens within a few picoseconds. There will be a few surface charges on the resistor R1, and these indicate its new status of potential. It should be clear that a voltmeter when connected between terminals A and B of circuit will read ‘0’ volts, because the potential of the resistor R1 and the battery positive, will be the same, namely, 12 volts. In the case of the resistor R2 connected to circuit zero, a few electrons would have entered the wire and the resistor R2 from the negative terminal of the power supply which is circuit zero, making the potential of the resistor R2 the same as circuit zero. There will be a few surface charges on the resistor R2 that indicates its new status of potential. A voltmeter when connected between terminals C and D of circuit will read ‘0’ volts, because the potential of the resistor R2 and the battery negative will be the same, namely ‘0’ volts. The current in the circuit will be zero because of the open circuit. Since the potential of terminal B is the same as that of A, its potential is 12 volts. Since the potential of terminal C is that of the battery negative or circuit zero (terminal D), it is ‘0’ volts. Therefore, a voltmeter connected between the terminals B and C will read the same p.d. as that between the terminals A and D namely, 12 volts. We can allow a current to flow in the circuit by simply connecting a wire between terminals B and C thus, short-circuiting them. The current in that case will be 12 V/(10 Ω +10 Ω) = 12 V/20 Ω = 0.6 amps. The two points marked on the x- (voltage) and y- (current) axes are joined together, and this line is called the “Load line” of the network. The load line is the locus of points, or pairs of voltage and current values for the voltage between terminals B and C and the current in the circuit, when the terminals B and C are bridged by a resistance. The load line is fixed for a fixed power supply voltage and fixed values of resistors R1 and R2. AC load line Circuit analysts usually draw ac load lines during the design phase of transistor amplifiers. In Section 3.4, Chapter 3 of textbook 4 in References in last frame of Video #1 more details including diagrams of the analysis of circuits using dc network load lines are provided. In the question Q.3.1 in the file "Additional Practice Questions for all chapters" in the CD with this textbook 4, a description of ac load lines is provided, which would be useful to read. Space does not permit a full discussion in this post.

How about common colector for increase current, is the q point and dc load still be calculated?

would it make difference if there was a RE resistor and R2 resistor under RB ?

When Vce comes negative...how will be the dc line...or the negative sign doesn't affect?

ty OCT!

What software do you use to draw all that ?

TNAK YOU

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There are 2 ways to bias the transistor...one way is to set Vce to half the supply voltage. The other way is determine Vce sat and Ic max then look at the middle Q point operating on the graph of the transistor characteristic. From that find the nominal hfe.

Thanks for the video Please i wish to know the software you used in writting in your video

Hello. are your playlist organized? like the first video is lesson 1 and the next video is lesson 2 like that

i wish if my teacher is as good as you

does q stand for quiescent? so the quiescent voltage is the voltage at the q point?

Is Vbe and vb the same?

11:45 is it always true - "potential between C and E is = half of Vcc" or in this particular example?

Do ACLL please

Can you do this video with PNP transistor

DO you have a powerpoint for this one?

how could we know that the IC value we choose is in the appropriate region ??

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Can we take beta value as random like 100,150,200..🤔

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I don’t know but m more confuse 😢

H

Thank you