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  • 6W Inductor Free Stereo BTL Class D Audio Amplifier Circuit Diagram

  • Created: Feb 21, 2016

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The audio amplifiers are amplifiers used to increase the amplitude of an audio signal that passes through it. This allows low power signal level to a level that is suitable for loudspeakers, maximizing the volume output. There are many classes of amplifiers; one of this is the class-D amplifier. The class-D amplifier converts an input waveform into a continuously PWM (Pulse-Width Modulation) analog signal by switching its transistor on and off. This class of amplifier uses a technique similar to PWM to control the output. The circuit is a class-D 6W inductor free audio amplifier for BTL (bridged-Tied Load) stereo speaker at up to 6Ω to 8Ω per channel. The TPA3144D2 has an advance EMI suppression technology with spread spectrum control and 1SPW modulation scheme that enables the use of inexpensive ferrite bead filters at the outputs.

The advantage of a class-D amplifier is its power efficiency; the TPA3144D2 has up to 90% efficiency at 8Ω, eliminating the need for a heat sinks. The reason of this is that the transistor function as a switch; they are either fully ON or OFF. Since the transistor is not partially conducting, but conducting fully and off; no power is wasted thus no heat is generated. The TPA3144D2 can operate in a single power supply between 4.5V and 14.4V. The PVCC capacitors should be low ESR type because they are used in circuit with high speed switching. The real capacitor opposed to the ideal can be modeled as a resistor in series with an ideal capacitor. This minimizes the beneficial effects of the capacitor in the circuit. Having a low ESR value, the more the real capacitor behaves like an ideal capacitor. The device can function in either BD modulation or 1SPW modulation. When 1SPW pin is ground it function as BD modulation, this allows operation without the classic LC reconstruction filter when the amplifier is driving an inductive load with short speaker wires. When 1SPW is high, it alters the normal modulation scheme so it can achieve higher efficiency with a slight penalty in THD degradation and more attention required in the output filter section.

The design is applicable in inductor free application with limited distance length of wire between the amplifier and speakers. It can be configured in stereo or mono mode, depending on the output conditions. It has a wide range of applications in televisions sets, mini speakers, and wireless and Bluetooth speakers.