cmon guys I need replies

 

I find it hard to belive that your professor just out of the blue gave you this assignment. You must have some books and lessons you can use as support. And Google is your friend. The members in this forum will also help you with advice, or discussion around circuit details. But we will not do your homework for you
Just a hint. Then you build an audio amplifier it is common to use several gain stages. The first stages usually provide voltage gain only. And the last stage will be the driver stage.

 

ok one more question if you can see in the diagram the input signal and output signal are out of phase, what should i do to make the phase of both the signals same???

Of course the signals are out-of-phase, the extremely simple darlington transistors are common-emitter which inverts. If you add another common-emitter single transistor at the input then the input and output will have the same phase.

I have to show the waveform first to my professor and then my job will be to implement this circuit on bread board and I will have to use mic as input signal and speaker as output, so tell me how many ohms speaker I should select and which type of mic???

Your extremely simple circuit will not work with a mic because its voltage gain is too low. It needs a preamp that can add voltage gain and can invert the signal.

Your extremely simple circuit operates in class-A which causes a high current to flow continuously in the output transistor and speaker which might cause them to overheat then fail. Audio amplifiers almost always use two output transistors operating in class-AB so that they do not have a high current flowing continuously and work very well. Speakers never have a DC current flowing in them like in your extremely simple circuit.

Most speakers are ..... ohms. You find out.
A very common type of mic performs very well and is inexpensive. It has been used for about 35 years. You find out.

 

well guyz I have to implement this circuit on bread board my teacher accepted it, well It will be easy for you not me as I am yet learning, so what do you think my amplifier will work properly or not?? which type of amplifier then I should select???

 

waiting for replies

 

Your circuit is too simple and needs you to scream into the mic for a low level sound to be produced by a speaker at its output.
If you make it on a breadboard with long wires all over the place then it might oscillate at a high frequency.

 

So U need a working amplifier. Class AB?

 

@ guru: so if I put the components on bread board make suitable connections so after supplying power will my amplifier work as it should???

 

@ Rifaa: if u can provide I will be grateful to you

 

OK ..let me see
First tell me have you got the power supply for it

 

This is my headphone amplifier that I design long time ago (1998).
And I build this circuit on a piece of cardboard.
And I add potentiometer to volume control and put 470uF capacitor across R13.
Vcc = 12V;
T1 = T2=BC548B,
T3 = T4=BD139
T5 = BD140

RL represents the speaker

 

Try this.
Couertesy of Rod Elliot.
Do not use other than for personal use


This amp can deliver 60W to an 8 ohm load.
Sound is excellent
Heatsink construction is critical for temperature stability.
Find the components and a good heat sink and I will explain how to mount the transistors and biasing diodes

Here is the link:
http://sound.westhost.com/project03.htm

 

Rifaa,
Please don't upload Rod Elliott's schematics to AAC.
Instead, provide a link to the project on his website.

Mr. Elliott is rightfully sensitive about fair use of the materials provided on his website. We do not wish to arouse his ire.

There is plenty of great information available for reading on his website, that should adequately cover the requirements for this project. I don't think there is a need to re-invent the wheel here.

A 60W amplifier is maximum overkill to power headphones. I don't know why you would recommend such a large and expensive project.

 

@ guru: so if I put the components on bread board make suitable connections so after supplying power will my amplifier work as it should???

No.
I said that its gain is much too low and if you make it on an intermittent breadboard then it might oscillate.

 

Hello,

@ SgtWookie,
I replaced the image to the link where R!f@@ has taken the image from.

@R!f@@,
There is a lot of useful material on the internet.
Elliots Sound Products is only one of them.
Please use the links without harming the rightful user.

Bertus

 

@jony: hey jony u haven't specified the value of V1 and mic also!!!

 

isn't there any simple class AB amplifier just like my class A amplifier having fewer components???

 

Hello,
@R!f@@,
There is a lot of useful material on the internet.
Elliots Sound Products is only one of them.
Please use the links without harming the rightful user.

Bertus

I have permission from Rod and He said I can provide his schematics here for educational use.
I don't see why you guys are making such a fuss.
His schematics are excellent for beginners as well as audiophiles.
I know, cause I have few of his ones built by my self and I am using them for a few years.
I will not use other peoples materials without their prior approval, haven't you read my posts.
I know there are other amps out there, I have done my research from the day I stared building amps, and his ones are by far the best I came across.
So I would rather suggest his than any other.

OP can see that site and from it he can learn how amps are build, None of here can provide the info that Rod had about building amps. The circuits are built by a lot of hobbyist around the world.

His circuits are without errors and so OP can be sure that the circuit would work and he doesn't have to came back here and ask what value should be and what transistor should be there.
If he is in doubt about the building process I am here to tell him how, cause I have built those.
I don't think most of the guys have his circuits built, since I do not see any one suggesting him anything that could work without hassle.

 

isn't there any simple class AB amplifier just like my class A amplifier having fewer components???

You can make a simple amplifier with an output of 0.4W into 8 ohms, about 2% distortion and not much gain with 3 transistors. But an amplifier IC costs less and has much better performance.

 

I am not allowed to use IC