一种适用于D类音频功放的全差分运算放大器

介绍了一种应用于超低EMI无滤波D类音频功放的全差分运算放大器结构,可构成积分器,起滤除高次谐波的作用。该运算放大器采用两级结构来获得高增益,第一级为折叠共源共栅,偏置电路采用反馈结构,给整个运算放大器提供偏置电流,从而提高电路的电源抑制比;采用伪AB类输出级提高运放的瞬态响应,稳定运放输出。仿真结果表明,该电路具有良好的性能:增益为113dB,相位裕度为67°;单位增益带宽为1.9MHz,共模抑制比为160dB,电源抑制比为82.7dB;共模反馈环路增益为120dB,相位裕度为62°。

A Fully-Differential Operational Amplifier for Class D Audio Amplifier

A fully differential amplifier for very low EMI filterless Class-D audio amplifier was proposed,which could be used as an integrator to filter higher-order harmonics.In this circuit,two-stage structure was adopted to obtain high open-loop gain,and a novel biasing circuit with negative feedback was used to achieve high PSRR.The output stage was designed as a pseudo Class AB to improve transient response and make the output stable.Simulation results showed that the amplifier had an open-loop gain of 113 dB with 67° phase margin,a unity-gain bandwidth of 1.9 MHz,a CMRR of 160 dB,a PSRR of 82.7 dB,and a common-mode feedback loop gain of 120 dB with 62° phase margin.