Audio amplifier is useful in electronics and it makes weak sound signals strong to run loudspeakers.
Class AB Stereo Amplifier Circuit are special as they mix Class B which is for good power use and Class A which is for good sound features.
Also, this article show a simple Class AB stereo amplifier which explains how it works, formulas, how to make it and what we can learn from it.
Circuit Working:
Parts List:
| Components | Values | Quantity |
|---|---|---|
| Resistors | 1k, 3.9k, 470k, 10Ω 1/4 watts | 1 each |
| 680Ω, 0.47Ω 1/4 watts | 2 each | |
| Potentiometer 4.7k | 1 | |
| Preset 1k | 1 | |
| Capacitors | Ceramic 10pF, 47nF | 1 each |
| Electrolytic 10μF 25V, 22μF 25V, 1000μF 25V | 1 each | |
| Semiconductors | Transistor 2N3904 | 2 |
| Transistor TIP31A | 3 | |
| Transistor TIP32A | 1 | |
| Loudspeaker 8Ω | 1 |
This Class AB stereo amplifier uses smart design with complementary transistors as it gives good power and clean sound and it also can run 8 ohm speaker with less distortion.
Here, TIP31A and TIP32A transistors help boost output and signal comes in through VR1 potentiometer to adjust input strength.
Then capacitor C1 blocks DC and lets only AC audio to go in.
After that, Q1 and Q2 2N3904 are differential pair and they give first signal boost and keep circuit stable, Q3 TIP31A and Q4 TIP32A are drivers and they make signal stronger for final stage and Q5 and Q6 both TIP31A work in push-pull.
This reduces crossover distortion and keeps amplifier efficient.
R3 sets Q2 base and C3 helps stability at high frequencies, R4 and R5 set bias current for drivers and R6 senses current and gives feedback for more stability.
Finally, C4 and C5 are decoupling capacitors as they clean power and reduce noise and we can adjust the idle (quiescent) current in output stage.
How to Build:
To build a Class AB Stereo Amplifier Circuit follow the below steps for connection:
- First, put all parts as shown in the circuit diagram
Q1 Connections:
- Then collector connects to third leg of VR2, base connects to center leg of VR2 and emitter connections to second leg of VR2
Q2 Connections:
- Now collector goes to emitter of Q1, base goes to C3 and R3 and emitter goes to GND
VR1 Connections:
- After that, center leg connects to negative side of C1, upper leg connects to audio input and third leg goes to GND
Q3 Connections:
- Next, collector connects to +30V, base connects to collector of Q1 and then emitter connects to emitter of Q4 through R4
Q4 Connections:
- Now collector connects to GND through R5 and base connects to collector of Q2 and emitter connects to collector of Q6 and emitter of Q3 and base of Q5
Q5 Connections:
- Then collector connects to +30V, base connects to emitter of Q3 and then emitter connects to collector of Q6 through R6
Q6 Connections:
- Also, base connects to collector of Q4, emitter connects to GND through R6
- Then R1 and R2 connect from collector of Q1 to +30V and C2 connects between R1 and R2 and also to R3 and base of Q2
- Now C4 connects from collector of Q6 and emitter of Q5 and one side of 8Ω speaker and other side of speaker goes to GND
- Lastly, C4 negative side goes to R8 and C5 in series of GND
Conclusion:
Overall, this simple and easy to make Class AB Stereo Amplifier Circuit is smart and helpful and it boosts sound well without wasting power.
Furthermore, it shows how push-pull works and gives both good power and clean audio, also if we follow the above steps and learn how it works we can build and change this amp for many uses.
Therefore, this circuit helps us grow in electronics and in audio skills.