The audio amplifier is used to amplify small input signals to allow the speaker to make a sound. The design of this audio amplifier is a Class A power amplifier with a bipolar junction transistor. The reason why I choose to use a BJT here instead of a MOSFET is that it has a lower current gain, which is desired in order to reduce noise and distortion. In my design of the amplifier, I used "voltage divider biasing" to reduce the effects of varying small-signal current gain. I also used coupling capacitors at both input and output to separate the AC signals from the DC biasing voltage, and a bypass capacitor to maintain the stability of the Q-point. The Q-point has been set close to the middle of the load line, where the collector voltage will be approximately half of the supply voltage, in order to optimize the behavior of the amplifier.

[References: https://learnabout-electronics.org/Downloads/amplifiers-module-02.pdf and "Electronics for guitarists"]


REFLECTION
By designing this circuit, I have applied knowledge of NPN transistors and circuit analysis. Through this work, I have also improved my skill in logic design and research.

The greatest obstacle I encountered is determining the values of each component in the circuit. To overcome this challenge, I spent a lot of time researching and reviewing textbooks to make the circuit work successfully.