In the circuit given below, I'm working on an audio amplifer. It is driving a 4-Ohm load (speaker.)
Input : 1.1V peak-peak sine wave of frequency 1Khz. Input dc = 12v
Output : 4-Ohm load. Gain = (8 peak-peak) / ( 1.1 peak-peak) = 7.2
Circuit Description :
This circuit is meant to amplify audio input from a typical smartphone audio jack.
Input stage of amplifer is driven by 2N3904 low power NPN. At output stage I have used TIP147 and TIP142 to amplify the signal. Input potentiometer is used to control biasing current of driving transistor at 34% of its value(1k potentiometer), it gives me optimal results, after that it starts to clip.
100uF(C4) bootstrap is also used to feed-back at R9-R2 junction increase the voltage gain. Rest are just biasing resistors and filtering caps.
Yellow = Output & Blue = Input
Q) What can I do to increase the gain of this circuit and consequently increase the output power (I don't want to increase supply voltage?)
Keeping this circuit in mind, also suggest me some better design options too.
Give me a heads up if other circuit specific information is needed to entertain my query.
Please bear in mind that this circuit is for my learning experience only. I know there are other more efficient ways to do what I am doing, but they are a bit advanced for me at this stage.