Techniques of pop-click noise suppression and saturation distortion compensation for class-D power amplifier

Abstract

The circuit techniques that suppress pop-click noise and reduce saturation distortion are presented for class D amplifier in mobile application. Pop-click noise level is effectively suppressed by detecting power voltage, controlling preamplifier and driver circuits of power stage in sequence, and providing discharge path between amplifier output and ground. Meanwhile, in class D power amplifier with feedback loop structure, the integrator is easy to saturate when a large amplitude signal is fed into the input terminal of the amplifier. Consequently, the saturation distortion is generated in amplifier output when the pulse width modulator fails to modulate input signal due to integrator saturation. The compensation technique in the pulse width modulator output can effectively reduce the saturation distortion, and also eliminate the risk of the transistor switch thermal damage due to power MOSFET still on state. The proposed class D amplifier with the above features was fabricated with 0.35 μm CMOS process. Pop-click noise level of 1.5 mV，THD+N of 0.025% can be achieved in 3.6 V power supply.

Keywords

• class-D amplifier
• filterless
• pop-click noise
• saturation distortion