circuit modification and help needed

Thread Starter

InnocentOfTheWorld

Joined Apr 15, 2010
47
dear friends,
i am attaching my circuit made in proteus as an power amplifier of 8 watt and speaker 8 ohm as load,which should work in audible frequency range.
My circuit contains only one capacitor tell me it's appropriate value and kindly after adjusting values do frequency and transient analysis on proteus. and tell me how to do these analysis on proteus. i did many times but they don't work i tried to adjust y-axis scale but i was unable to adjust it may be problem in my software :(
and also tell will this circuit work for 8 watt?
anyone reply
if you have questions ask me
 

Attachments

Last edited:

bertus

Joined Apr 5, 2008
20,061
Hello,

Bumping is NOT needed.
This is an international forum, so responses can take hours to even days.
Not all have proteus, so post the schematic as a .PNG over here.
Then others can also have a look.

Bertus
 

simo_x

Joined Dec 23, 2010
200
Is not a simulator which tells you if the circuit will work in our real world, but only your knowledge about electronics.
However, why you are not planning to do it with operational amplifiers instead of using all these transistors?
 

SgtWookie

Joined Jul 17, 2007
22,201
So, it is a homework assignment from your instructor or professor?

I'll tell you one thing, your 2N4401 and 2N3906 transistors you are using in the output section will not be adequate for the current that you will need. 2N3906 transistors are rated for up to 200mA collector current maximum, but 100mA is more of a practical limit. If you want 8 Watts output power, you will need 1A current through an 8 Ohm load, which is 10x the practical limit of the 2N3906.
The 2N4401 is better, but still woefully inadequate.
 

Thread Starter

InnocentOfTheWorld

Joined Apr 15, 2010
47
here is a new design i tried to made although working on proteus and giving the output as i am not much experienced tell me if there is anything which needs to be modified for better results.also proteus files are provided.yes it is a home task

P.S
now used tip122 and tip127 in output stage


8 watt.png
 

Attachments

Georacer

Joined Nov 25, 2009
5,154
By now you should know the AAC forum policy. Post your work and efforts on solving your problem in order to receive any help.

Can you identify any amplification modules in your schematic?
 

Thread Starter

InnocentOfTheWorld

Joined Apr 15, 2010
47
yes at input it is common emitter amplifier
and output is class ab amplifier
i want to know about the intermediate stage and how current amplification is achieved in that part
 

Audioguru

Joined Dec 20, 2007
11,251
Your schematics have a dark grey background and a grid all over them which makes them hard to read.
None of the connections have a dot so where lines cross it is impossible to see if they are connected or not.
Some of thye text is impossible to read.
 

bertus

Joined Apr 5, 2008
20,061
Hello,

I merged the threads as they are about the same circuit.
Please do not start new threads when the other one is still active.

Bertus
 

Audioguru

Joined Dec 20, 2007
11,251
Most power amplifiers except yours are DC-coupled but have an input coupling capacitor.
All power amplifiers except yours have DC and AC negative feedback.

It would be useful for you to look at some power amplifier circuits found in Google.
 

Audioguru

Joined Dec 20, 2007
11,251
tell me how it amplifies current
Didn't you learn about transistors?
The darlington output transistors have a current gain of at least 1000 times and typically 4500 times.
The peak current in an 8 ohm speaker with 8W is 1.4A so the base current is only 0.3mA or less to 1.4mA.

The first transistor has a current gain of a few hundred. I can't read its tiny blurry part number. I also cannot read its tiny blurry resistor values.
 
Top