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help bulding BJT amp

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That's a car radio chip, and provides 4W per channel stereo, or 16W bridged mono.

This is a pretty crude amplifier, you would need two of them to replace the IC.

**broken link removed**
 
Assuming you're wanting stereo, you don't - to bridge them in mono you'd just need to provide anti-phase feeds to them, and connect the speaker across the two outputs.
 
Assuming you're wanting stereo, you don't - to bridge them in mono you'd just need to provide anti-phase feeds to them, and connect the speaker across the two outputs.

i want to do mono ,can you please explain how to do that ,it is to advanced for me .

thank you for your help
 
i have updated my first circuit by adding an emitter follower so the circuit can drive the 4ohm load..in the simulator the circuit is working fine ,but when i tested it i got few problems
first the supply voltage drops from 15v to 7v. also transistor Q2 got very hot ??



**broken link removed**
 
Measure the current in R1. Calculate the power. (If you don't want to burn your fingers do this in the simulator first.)
 
i have updated my first circuit by adding an emitter follower so the circuit can drive the 4ohm load..in the simulator the circuit is working fine ,but when i tested it i got few problems
first the supply voltage drops from 15v to 7v. also transistor Q2 got very hot ??

You've completely ignored everything you've been told, it wasn't a power amplifer before, and it's still not one now - refer to the circuits you've been told about before, notice that NONE of them look anything like your effort.
 
Look in Google at audio amplfier circuits and class-A (the output transistor gets very hot), class-B (two output transistors do not get very hot but produce crossover distortion) and class-AB (two output transistors also do not get very hot but have low distortion).
 
its not that am ignoring what you have told me ,but the circuit that i got i didn't understand it and i already said that i want to learn not just copy . plus the previous circuit gain is only 10 i need 20 and how can i change it if i don't understand it .

i have been told by HERO999 that the problem with my circuit is the output impedance so i tried to match it using emitter follower.


since my circuit is totally wrong ill go back to the previous one **broken link removed**.
**broken link removed**


from what i understood that region 1 is the class AB that every one been telling me to use right?
region 2 is class A ,now what i totally don't understand is the purpose of Q3? the connection between Q1 and Q2,Q3 through R11?and the variable resistor R4?and how i can increase the gain ?

note:
am required to design an amplifier so i should be able to match the requirements given and be able to explain the purpose of every component that i used ...

actually my lecturer he is the one suggested to me to use the emitter follower ,if he is wrong i cant tell him that and if he is bad or simply don't know electronics i cant tell him that either but i need to make my circuit work so please go easy on me with criticism.
 
Q3 and Q4 are both upside down, it should make more sense if you wire them correctly. The preset is used to set the quiexcent current, and the gain is set by the ratio of R10/R11.
 
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