Pls. tell how you have calculated Fc of 49Hz with 10ohms internal emitter resistance (re) of the transistor.??

Fc = 1/ ( 2 * pi * R * C ) = 0.16/(R*C) = 0.16/( 10Ω* 330uF) = 0.16 / 3.3ms = 48.4848485Hz

 

Pls. tell how you have calculated Fc of 49Hz with 10 ohms internal emitter resistance (re) of the transistor.??

I told you the formula before. The same formula is used to calculate the cutoff frequency of the input coupling capacitor and the output coupling capacitor.

 

I am very thankful for your useful post...!!

 

I am very thankful for your useful post...!!

But why doesn't your teacher teach about this simple and important stuff??
Why doesn't your textbook show it??

 

The O/P is I think pulling a scam on you guy's. He also posts on ETO under the same name asking the same questions! On ETO he also has a listing for his website, as I posted in post #93.

His tagline, " Genius is 1% inspiration and 99% perspiration" should be, 1% his inspiration, 99% your perspiration.

 

Most Indian schoolkids post the same questions on many Western websites.
They also send millions of PMs.

 

Is there any software from which i can connect output directly to computer??

 

Is there any software from which i can connect output directly to computer??

Why do you want to connect the output of a single transistor to a computer?
The simulation program shows the output.

 

You folks have unquestionable patience. Have started tutoring from physics of transistor to its application. If nothing is taught in the college then what is doing there, piling questions???

 

Most Indian schoolkids post the same questions on many Western websites.
They also send millions of PMs.

what does PM stand for?

 

PM = Private Message, kind of like an e-mail sent directly through the forum.

I got really mad at the original poster and a lot of others from his country quite a while ago but eventually realized they must not really have much of an educational system around there, probably why I encountered so many foreigners in my many years of college (twice) who were lucky enough to get over here and had the finances to pay for it. Perhaps if he learns enough on his own he'll earn a scholarship to a far more fitting school as he's going to extremes trying to learn electronics.

Who am I to judge? I taught a bit of Physics the second time I was back at the University. I worked for the Physics department, specifically the Center for Laser and Photonics Research at OSU/Stillwater, but at times a professor or grad student that conducted the lectures would get sick/other and I got called in as a substitute. It was always fun to find out where they were at and the first several days (and sometimes after hours at night) were spent getting getting the confused or slackers all on the same plane so I could move forwards in the lectures.

 

PM = Private Message, kind of like an e-mail sent directly through the forum.

but eventually realized they must not really have much of an educational system around there,.

I don't know, google electronics lectures, videos, there is among others a India educational classes, like college classes, that you can view on line, as there professor is teaching it, these teachers, are teaching modern transistor theory electronics, right down to hybrid parameters and modeling transistor parameters, they are well educated teachers in there field.

 

If so I think we've got a combination of a language barrier and a number of other things that might enter into the equation.

He's calmed down to the fact that he needs to learn everything from the beginning and with the persistence he has I'm hoping he'll spend more time in practice rather than theory. From what I understand even the most basic parts are hard to come by down there which severely limits experimentation as we know it. I sit here and if I place an online order to Mouser I've got it the next day for a few $ shipping which is usually better for me than trying to go through the frustration of Radio Shack not having much more than cell phones anymore.

I can watch that online stuff only for so long, over the years I found nothing beats building your own stuff and failing 90% of the time at first but I've been at this for well over 50 years.

I would love to hear some specifics as to where Rritesh is studying and what his plans are for the future. Anyone with an inquiring mind should not be ignored but encouraged if he genuinely demonstrates a willingness to learn as he has over the time he's been posting here.

I would rather that he read the e-book, preferably printing it out and going to bed with it but it may be hard for him to read English thus Google Translate may be an option. It may not capture half of it word for word but it's better than nothing.

We don't know his background so resources may be extremely limited to him and he's fighting to learn this stuff but he jumped in way too early on complex stuff when he really needed to learn about the most simple basics before he advanced to even simple transistor amplification. I say let's give him some time as his questions have become a bit more reasonable as he's starting to learn our language, but I'd really rather that he would type more in his questions rather than tell me why please.

 

over the years I found nothing beats building your own stuff and failing 90% of the time at first but I've been at this for well over 50 years.

but he jumped in way too early on complex stuff when he really needed to learn about the most simple basics before he advanced to even simple transistor amplification. .

I agree,

The start of my learning came mostly by buying one of those old Radio shack sets, the 160 in 1 set, which had a lot of discrete components to work with, as you were saying about hands on approach, I agree, nothing beats experimenting to realy get a grasp at the real world designs with this stuff.

When I got that lab, I hardly knew anything about electronics, so I would build a circuit with there instructions, then from there I kept a notebook handy, and began to take out components one at a time, to see if the circuit still worked,
if it did then I took out another, and so on, if the circuit didn't work, I replaced the same component, then took out another one,

I did this until the circuit could not work anyfurther whithout another component taken out, so now I have it to it's most simplest form,

then from there I would start experimenting changing values, and things, and kept a log of what the circuit did. I tried to understand how the circuit worked at it's simplistic form.

That way it was easier to understand how the components contributed to the circuit, to make it work.

It came to a point, where I had to replace transistors so much, that I just stuck the legs through the springs at the top of the board, knowing it will be easier to change it that way.

My transistors were never put into the lab on a permanent basis anymore, cause I knew I would burn them out soon enough.

But experimenting along with reading as much basic electronics books possible, is a good approach to having a more better understanding on this subject.

 

I understand that you are in 3rd semseter B.tech. By know you should have come across the transistor theory twice, once in your pre-university where they deal with the physics of transistor in depth and then in your 1st semester (or 2nd semester depending on the college) of B.Tech where need of biasing, different techniques of biasing, configuration like cb,ce,cc , stabilizing, cascading etc is dealt in decent depth. All engineering colleges in India should mandatorily be approved by AICTE( All India council of technical education) and their standard text books deal this subject in excess. How is that you have missed all this.
People on this forum have come out of the way and helped you in understanding all your trivial questions, please don’t misuse the forum and don’t take them for granted because you are getting it for free.
Any resource, be it human, natural, monetary is to be consumed judiciously for our own good. 5000 odd year old culture of our country should have taught you this at least, if not transistor basics.
Hope you take it in right spirit.

 

Before you leap into phase shift oscilators, and darlington configs. and bootstrapping,
It is apparent from the schem. in this post, you are stumbling on getting a transistor biased into its linear region.

Follow these steps to see how this schem. is not designed properly.

First you have 10v. supply.
[(V1 x R2) / (R1 + R2)] = 4.44v. equals base voltage.
Now subtracting Vbe of 0.65v. from this base voltage , you now have around 3.8v., this is the voltage across the resistor labled R4, which is 500 ohms.

Now the current through R4 is (3.8v. / 500 ohms) = 7.6mA.

For first order aproximation, assume that current value to be the current that will also flow through R3, which will produce a voltage drop of, (7.6mA. x 2K ohms) = 15.2v.
You are only using a 10v. supply, so it is impossible to use these resistor values.

If you want a basic approach to this design here is a way to do it.

Kepping your 10v. and using the value of 7mA. for collector current.

Since you are biasing this into its linear region, then use this rule of thumb.

Make the voltage drop 1/2 of the supply voltage, across the collector resistor. So design this with 5v. across R3.
therefor R3 will = (5v. / 7mA.) =~ 680 ohms.

Now to solve for the emitter resistor R4, design this to have 1V. drop across the transistor itself.

That means the voltage that is left will be across R4.
Voltage across R4 = (10v.VCC - 5v.R3 - 1v.transistor) = 4v. left over to be across R4. which is called "VE"

Now with 4v. across R4, VE, you can solve the value for R4, by using this equation, R4 = (VE / IC), where IC was established in the beginning of this excersise to be 7mA.
So R4 = (4v. VE / 7mA. IC) =~ 560 ohms.

Now for this to work, you have to establish the voltage divider resistors that will put a voltaqge at the base to cause the transistor to be turned on, here is how it is done.

Base voltage (VB) = emitter voltage (VE) plus Vbe (0.65v.)
given as VB = (VE + 0.65v.) = 4.65v. which will be applied to the base of this transistor, to make it turn on, and produce close to the current value of 7mA. that this is being designed for.

To solve for the resistors needed to make this happen, you need to use some more equations.

First make R2 to be around 10 times greater than R4.
So R2 will equal 560 ohms times 10, which would be 5.6K ohms.

Now to solve for R1 use these two equations.

Solve for divider current, first, by taking this equation here.
(divider current (ID), equals , base voltage (VB) divided by R2.
given as ID = (VB / R2) = (4.65v. / 5.6K ohms) = 830uA.

Now R1 can be solved by using this additional equation,
R1 = [(VCC - VB) / ID] = [(10v. - 4.65v.) / 830uA.] =~ 6.2K ohms.

Now build this circuit on your computer and check the voltages with respect to ground, at the collector and the emitter and the base, and see if they are close to the calculated values in this excersise.

Once you do that, THEN, follow the same procedure outlined, BUT THIS time make the voltage drop across the transistor to be 2.5v. and solve for the values of the resistors R4, R2, and R1. in that order.

And again simulate it and check the voltages as you did before, then as a final excersise use 2.5v. across the transistor again, but THIS TIME make the collector current (IC) be 10mA instead of the 7mA, you were using, and solve for the resistors R3, R4, R2, and R1 in that order.
Using the same techniques as given above.

Then let us know how you did, post your results for us to evaluate how you did on this.

Then we can show you how to modify these circuits to get voltage gains so it would act as an amplifier.

to find it base current, current in (R3-R4) is this right,

And how to know β for this ckt.??

 

to find it base current, current in (R3-R4) is this right?

Yes.

how to know β for this ckt?]

Simple arithmatic shows the amount of base current: 675uA - 648uA= 27uA.
Each transistor has a different β, even if they have the same part number.

This transistor has a base voltage of 648uA x 2.9k= 1.88V then its emitter voltage is about 1.88V - 0.7V= 1.18V then its emitter current is 1.18V/400 ohms= 2.95ma then its collector current is 2.95mA + 27uA= 2.98uA. Then its β is 2.98uA/27uA= 110.4. This number is approximate because we don't know the part number of the transistor so we cannot look on its datasheet for its typical Vbe voltage. This voltage also changes when the temperature changes and it is probably hotter where you are than the temperature where most other electronics geeks are.

EDIT: My collector current calculation is wrong. See my next post.

 

Yes.


Simple arithmatic shows the amount of base current: 675uA - 648uA= 27uA.
Each transistor has a different β, even if they have the same part number.

This transistor has a base voltage of 648uA x 2.9k= 1.88V then its emitter voltage is about 1.88V - 0.7V= 1.18V then its emitter current is 1.18V/400 ohms= 2.95ma then its collector current is 2.95mA + 27uA= 2.98uA. Then its β is 2.98uA/27uA= 110.4. .

Hi,
Audioguru,

For the sake of him not getting confused, please rewrite the above, to show him the correct value of the emitter current and collector current.

I know youll see it when you look back over it again.

 

I understand that you are in 3rd semseter B.tech. By know you should have come across the transistor theory twice, once in your pre-university where they deal with the physics of transistor in depth and then in your 1st semester (or 2nd semester depending on the college) of B.Tech where need of biasing, different techniques of biasing, configuration like cb,ce,cc , stabilizing, cascading etc is dealt in decent depth. All engineering colleges in India should mandatorily be approved by AICTE( All India council of technical education) and their standard text books deal this subject in excess. How is that you have missed all this.

I've seen people go through four years of theory (in all sorts of subjects) yet still not understand a minute of it, they only memorized the formulas, dates or whatever just to pass the tests. Labs in electronics or physics were often a joke as you were paired up into groups and one usually ended up dominating the solution from which the others copied.

As mentioned and repeated above by another there is no replacement for true hands on experimentation on your own. I was lucky as a kid when all I had was vacuum tubes to deal with which are far more forgiving, when transistors first came out I was baffled trying to get even the simplest circuits to work. 2N107, 2N170 & CK722 were my first (had to beg to get them to mail order them for me) but in time I was able to get them to operate as simple amplifiers then later as an AM transmitter with the help of books and magazines. I didn't like them that much so I stuck with my tubes and piles of parts salvaged from old TV sets. Not many 8 year old kids had home built 400V power supplies sitting around but I did as my parents had no idea of what I was doing and I built my first one when I was 6 from TV parts. I probably burned up more tubes and resistors than you can imagine from mis-designs but learned from my mistakes every time.

I would assume things are the same now. You just need a good stock of parts and some bench equipment to learn and never expect anything to work perfectly the first time or possibly for many times after that.

 

Hi,
Audioguru,

For the sake of him not getting confused, please rewrite the above, to show him the correct value of the emitter current and collector current.

I know youll see it when you look back over it again.

OOps,
When the emitter current is 2.95mA then the collector current is 2.95mA minus the 27uA base current so the collector current is 2.92mA. Then the β is 2.92mA/27uA= 108.2