A driving amplifier capable of operating at a minimum voltage is proposed, aiming to subdue the distortion effect caused by large amplitude driving at the hearing aid loudspeaker. Since the linearity of a cascode amplifier usually degrades with the reduced supply voltage, a three-stage cascade amplifier having a parallel cascade second stage, and a folded cascade Class-AB output current control in place are designed. With such an arrangement, the open loop gain should still be maintained at a sufficiently high level even in the presence of increased output amplitude. Also, the minimum supply voltage required can then be reduced to merely |VGS|+2|Vdsat|. Fabricated on a 0.18μm complementary metal oxide semiconductor (CMOS) process, the proposed amplifier achieves −72dB total harmonic distortion (THD)+noise(N) with a loudspeaker load of 100ohm while operating from a 1.2V supply and being subject to a 1kHz sinusoidal input.

中文翻译：

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具有自适应三级开环增益和折叠级联 AB 类输出电流控制的最小电压驱动放大器

提出了一种能够在最小电压下工作的驱动放大器，旨在抑制助听器扬声器大振幅驱动引起的失真效应。由于级联放大器的线性度通常会随着电源电压的降低而降低，因此设计了具有并联级联第二级的三级级联放大器和折叠级联 AB 类输出电流控制到位。采用这种布置，即使在输出幅度增加的情况下，开环增益仍应保持在足够高的水平。此外，所需的最小电源电压可以降低到仅|五GS|+2|五卫星|. 在 0.18 上制造μm 互补金属氧化物半导体 (CMOS) 工艺，所提出的放大器实现-72dB 总谐波失真(总谐波失真)+噪音(ñ)扬声器负载为 100欧姆，而从 1.2 操作V 电源并受到 1kHz 正弦输入。