Here is a new audio power amplifier schematic built around TIP darlington pair transistors. You can use this circuit for home audio power amplifiers and car audio amplifiers. The TIP142 and TIP147 darlington pair transistors forms a push pull high power amplifier configuration while the two BC558 PNP transistor provides a mini audio pre amplifier circuit. The audio signal is applied to the pre amp through a capacitor, then it is coupled to the push pull power amp via TIP141 transistor. The values and ratings of different components of power amplifier design are also given in this article. Implementation cost of this mini audio amplifier circuit is too cheap, near $5. The circuit can deliver 150 W RMS to a 8 Ω (150 Watt power amplifier).
Circuit diagram audio amplifier
Click on the circuit for enlarged view
- Transistors (TIP141; TIP142; TIP147; BC558 x 2)
- Resistors 7 watt(0.33Ω x 2)
- Resistors 1 watt (3.3kΩ x 2)
- Resistors ¼ watt (22kΩ x 2; 220Ω; 1.5kΩ; 33Ω; 27kΩ)
- Capacitors 50V (100µF; 10 µF x 2)
- Speaker (8Ω, 150Watt)
Working of 150 watt amplifier
- Our new audio power amplifier project is based on TIP 142 and TIP 147 (complementary darlington pair power transistors which can handle 5 A current and 100V).
- The two PNP (BC 558) transistors forms a pre amplifier section to the preceding high power push pull amplifier built around TIP141, TIP 142 and TIP 147 darlington pair transistors.
- We are using 2 PNP transistors to form a preamplifier section, it is nothing but a differential amplifier to improve overall performance of the amplifier. The application of a differential amplifier in the input phase reduces noise.
- Input signal is applied to the differential amplifier section via 10µF DC decoupling capacitor. Capacitor removes the DC voltage from the input audio signal.
- 10kΩ potentio meter is used for volume controlling.
- Feedback voltage is applied through the 22K resistor.
- A complementary class AB push pull power amplifier stage is built around the TIP darlington pair transistors to drive the 8Ω 150 watt speaker (The circuit can deliver 150 W RMS to a 8 Ω).
- The diodes (1N4007) biases the complementary pair and guarantee class AB amplifier configuration.
- Transistor TIP141 drives the push-pull pair (TIP142 & TIP147) and its base is directly connected to the collector of pre amplifier stage.
- +/-40V, 5A dual power supply is necessary to provide supply for this simplest amplifier circuit. Use 30V-0-30V step down transformer and construct a dual lab power supply for this project.