Audio Power Amplifier

Introduction

This project is about creating a prototype of an audio power amplifier using basic electronic components on a printed circuit board. This was one of my undergraduate laboratory projects as an Electronics Engineering student. I worked on this project with 4 other group members named Keith Decano, Tinie Lim, Lambert Lugtu, and Karl Rivera.

An amplifier is an electronic device that can increase or amplify a low input signal (sound) to a higher output signal. The basic concept of this project is similar to loudspeakers, bass speakers, guitar amplifiers, etc. The audio amplifier in this project is a push-pull audio amplifier which uses two transistors for the positive and negative signal to reduce any causes of distortion. A 9 Volts DC adaptor is used to bias the amplifier circuit.

Components & Materials

Schematic Diagram

The audio amplifier circuit is designed with two stages. The first stage is a simple common emitter transistor which is the most efficient use of a single transistor for power amplification. The second stage is a push-pull. It can be also called phase splitters where it provides the input signals to a single-stage amplifier that uses two transistors, one for the positive amplitude and second for the negative amplitude. The two outputs of each transistor are out of phase by 180 degrees with each other. This allows more gain than one transistor could supply itself. This push-pull amplifier is used where higher output power is needed.  This makes it more efficient than any other amplifiers.

The schematic diagram of our audio power amplifier is shown on figure 1. The actual prototype is on figure 2. In this figure,the input of the audio amplifier will come from any electronic devices that can be connected to a jack like mobile phones, laptops, and more. The circuit is connected in the printed circuit board. The DC supply is an adaptor from AC to a 9 volts DC. The output will be produced by the speaker.

Simulation

Testing

Full Set Up

Conclusion

After running the system, the finding obtained from the prototype is that the output sound produced by the amplifier is distorted when using low amount of voltage (V_cc). Below are few factors of distortion of output sound:

• The required number of states is not greater than or equal to the designed state. In this project’s case, only 2 states were designed where the number of state required is actually 3 or more.
• Increasing the capacitor may result in decreasing possibilities of distortion of the output sound provided that the designed state is greater than or equal to the required state.
• The current needed must be more than 1 to 2 Amperes for the prototype.