Ways to suppress click and pop for class D amplifiers

作者：Wang Haishi Zhang Bo and Sun Jiang State Key Laboratory of Electronic Thin Films and Integrated Devices University of Electronic Science and Technology of China Chengdu China

来源：半导体学报, 2012, (08): 107-111.

• class D amplifier
• click and pop
• fast turn on
• fast charging
• dummy switch

<正>Undesirable audio click and pop may be generated in a speaker or headphone.Compared to linear（class A/B/AB） amplifiers,class D amplifiers that comprise of an input stage and a modulation stage are more prone to producing click and pop.This article analyzes sources that generate click and pop in class D amplifiers,and corresponding ways to suppress them.For a class D amplifier with a single-ended input,click and pop is likely to be due to two factors.One is from a voltage difference(KDIF) between the voltage of an input capacitance(Vcin) and a reference voltage(Vref) of the input stage,and the other one is from the non-linear switching during the setting up of the bias and feedback voltages/currents（BFVC） of the modulation stage.In this article,a fast charging loop is introduced into the input stage to charge FCIN to roughly near VREF.Then a correction loop further charges or discharges VCIN,substantially equalizing it with KREF.Dummy switches are introduced into the modulation stage to provide switching signals for setting up BFVC,and the power switches are disabled until the BFVC are set up successfully.A two channel single-ended class D amplifier with the above features is fabricated with 0.5μm Bi-CMOS process.Road test and fast Fourier transform analysis indicate that there is no noticeable click and pop.

• 出版日期2012-8-15
• 单位电子科技大学