A Simple audio amplifier (or power amp) is an electronic amplifier, that amplifies audio signals before sending them to a device like a headphone, or to a sound output that transmits it out through a speaker, radio device, or a wireless transmitter.
Audio amplifiers make the signal audible to the audience. Whether it is a recorded voice clip, live music, or the mixed audio of an entire group of people. They are the final electronic stage in a model audio playback chain before the signal transmits to the loudspeakers & speaker enclosures. In this project, we are going to build a simple amplifier circuit using two transistors.
Hardware Components
The following components are required to make Audio Amplifier Circuit
| S.no | Component | Value | Qty |
|---|---|---|---|
| 1. | Breadboard | – | 1 |
| 2. | Battery | 9v | 1 |
| 3. | Connecting wires | – | 1 |
| 4. | Condenser MIC | – | 1 |
| 5. | Speaker | 4 ohm | 1 |
| 6. | Transistor | BC108 | 2 |
| 7. | Resistor | 180KΩ, 4.7KΩ, 100KΩ | 1,1,1 |
| 8. | Ceramic Capacitor | 0.1μF, 10uF | 1, 2 |
BC108 Pinouts
For a detailed description of pinout, dimension features, and specifications download the datasheet of BC108
Audio Amplifier Circuit
Working Explanation
Audio input is provided via an audio transducer such as a Condenser microphone, which will turn the audio signal directly into an electrical signal. A 10μF capacitor is attached to the input to block DC components of the transmissions, Allowing AC components of the input to pass through.
A 4.7KΩ resistor offers the necessary biasing to the condenser microphone. Transistor Q1 is set up as a collector to base biasing function, by connecting a 180KΩ resistance. This resistor offers negative feedback for the transistor Q1. The output of Q1 reaches the collector of Q2, serving as an input. The 10μF capacitor eliminates DC voltages due to the biasing of Q1. Transistor Q2 acts as a fixed bias by using a 100kΩ resistor. Also, it offers additional amplification. The 10nF electrolytic capacitor likewise blocks the DC voltages of this particular biasing of transistor Q2 & delivers the audio output on devices such as headphones.
Applications
- Mainly used in the music industry such as audio frequency amplifiers & headphones.
- An important part of the home entertainment audio systems.
- Also used in the military for advanced warfare applications such as acoustic weapons.
- Also used in electronics such as interactive toys, Robots & Hi-Fi devices.
