Low Power Circuit Amplifiers!

Thread Starter

PaulEngineer

Joined Dec 21, 2016
159
Hello!

Glad to see you all again!

So, wondering and self questing about this theme for a long time, i ask myself, what could happen, if getting an amplifier push-pull and change the transistors, on the circuit board? Will it change something? I know it is weird and kinda stupid question, but i need to find it out! For example i would like to build the amplifier of HackTheWeek which is AB class push-pull amplifier! I think that will be the best practice for me! So the circuit schematic is in attachment! I have 3 transistors BC 141, BC 161, and BC 441! If i will replace them, could anything happen?
 

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Alec_t

Joined Sep 17, 2013
10,424
Those should be better than the 3904 and 3906 since they can handle more current. However, if you drive an 8Ω speaker at maximum amplitude with that amp and the battery is fresh you may be driving the transistors intermittently beyond their rated maximum current.
 

Thread Starter

PaulEngineer

Joined Dec 21, 2016
159
Wow really? Wooow! i didnt knew that! Its awsome! But there's one "but": That means, that if i put these transistors, on the circuit (I mean BC type) and apply the power required for their function, other components could be fail because of high warm? I have read the data sheets of each BC transistor and found that each of them needs around 3,7W max power dissipation (which means around 2W power dissipation so as to avoid overheat) so they could operate properly with great results on the sound! But im worry about the other components! Can i ask something optional? Is there any way on how to calculate, which resistors, capacitors is needed so the circuit could work properly?
 

AlbertHall

Joined Jun 4, 2014
8,486
Depending on the gain of the leftmost transistor in the circuit you may need to adjust the value of the 100k resistor to get the output voltage to be half the supply voltage for maximum undistorted output.
 

Thread Starter

PaulEngineer

Joined Dec 21, 2016
159
That helps a lot! Thanks! If someone would like to tell his/shis opinion, i am ready to get these opinions! Its very helpful for me! But thanks AlbertHall! Your answer help me a lot (i dont know if i said it correctly, cause im not good at english :D)
 
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