Amplifier Circuit Diagrams

150 Watt Amplifier Circuit – DIY Guide to Build Amplifier

Low Cost 150 Watt Amplifier Circuit

We’re going to make a simple 150-watt amplifier circuit in this project.


In my opinion, this is one of the most budget-friendly 150 Watt amplifier circuits you can assemble. This design, employing two robust Darlington power transistors, namely TIP 142 and TIP 147, is capable of delivering a substantial 150 Watts RMS to a 4 Ohm speaker. Are you ready to experience some powerful sound? Then, give this circuit a try!

The TIP 147 and TIP 142 transistors are complementary Darlington pairs renowned for their resilience, boasting a current rating of 5 amps and a voltage rating of 100 volts. In this setup, TIP 142, TIP 147, and TIP41 (Q1, Q2, Q3) handle the task of driving the speaker, while two BC 558 transistors (Q5 and Q4) serve as preamplifiers. The construction of this circuit is designed to be exceptionally robust, making it suitable for assembly on a perf board or through direct pin-to-pin soldering. To power the circuit, you can use a +/-45V, 5A dual power supply. I assure you, this circuit performs flawlessly!

The preamplifier section of this circuit revolves around Q4 and Q5, forming a differential amplifier. Utilizing a differential amplifier in the input stage effectively reduces noise and enables the application of negative feedback, thereby enhancing the overall performance of the amplifier. The input signal is fed to the base of Q5 via the DC decoupling capacitor C2. Simultaneously, the feedback voltage is routed to the base of Q4 from the junction of 0.33-ohm resistors through a 22K resistor. For driving the loudspeaker, a complementary Class AB push-pull stage is constructed around transistors Q1 and Q2. The biassing of the complementary pair is managed by diodes D1 and D2, ensuring proper Class AB operation. The push-pull pair receives its drive from transistor Q3, with its base directly connected to the collector of Q5. This circuit functions admirably and is worth trying out!

Circuit Diagram & Parts List.150 watt amplifier circuit diagram

PCBs for this project are available from PCBWay. Soon, we’ll post a sample PCB file (for download).


  • TIP 142 and 147 are Darlington pairs to remember. For clarity, they are depicted in the picture as ordinary transistors. So don’t be perplexed. Even though each one has two transistors, two resistors, and one diode, only three pins, base emitter, and collector, are visible. Internally, the rest are linked. As a result, it’s perfectly OK to treat each of them as a transistor for the sake of simplicity.
  • Use a power supply that is carefully regulated and filtered.
  • If you need volume control, connect a 10K POT in series with the input.
  • The wiring diagram does not indicate this.
  • All electrolytic capacitors must have a minimum voltage rating of 50 volts.

Power supply for this circuit.

The power source for this amplifier project is presented below as a +40/-40 unregulated dual supply. This power supply is only capable of supplying one channel; for stereo applications, double the transformer, diode, and fuse current ratings.

TIP 142-TIP 147 Pin Out Diagram with Schematics



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