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This paper presents a fully differential class-AB current mirror OTA that improves the common-mode behavior of a topology that presents very good differential-mode performance but poor common-mode rejection ratio (CMRR). The proposed solution requires a low-current auxiliary circuit driven by the input signal, to compensate the effect of the common-mode input component. Simulations in 40-nm CMOS technology show a net reduction of common-mode gain of more than 90dB without affecting the differential-mode behavior; a sample-and-hold amplifier exploiting the proposed amplifier has also been simulated.

This paper presents a supper class-AB adaptive biasing bulk-driven amplifier for ultra-low-power applications. In the proposed structure, two bulk-driven flipped voltage follower (FVF) cells are reconfigured as nonlinear tail currents using quasi-floating gate method to enhance transconductance and slew rate. In addition, two idle current controllers are employed as common source amplifiers to provide a supper class-AB structure without increasing total current consumption. The proposed structure is simulated in 0.18-$\mu$m CMOS technology at 0.5V supply with 35nW power budget. The results show a 57.9dB DC gain, 8.8kHz gain bandwidth and 38.2V/ms slew rate for the proposed amplifier.

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 $|V_{\mathrm{\text{GS}}}|+2|V_{\mathrm{\text{dsat}}}|$. Fabricated on a 0.18$\mu$m complementary metal oxide semiconductor (CMOS) process, the proposed amplifier achieves $-72$dB total harmonic distortion $(\mathrm{\text{THD}})+\mathrm{\text{noise}}(N)$ with a loudspeaker load of 100ohm while operating from a 1.2V supply and being subject to a 1kHz sinusoidal input.