An analog correlator based CMOS analog front end with digital gain control circuit for hearing aid devices

Abstract

In this paper, an analog correlator based analog front end with gain control circuit for hearing aid devices is designed and fabricated with 0.18 $$\upmu \mathrm{m}$$ CMOS process. The proposed analog front end consists of an analog correlator comprised of a multiplier, an integrator, and a mixed mode variable gain amplifier. The analog correlator is utilized to ensure the low input referred noise. A gain control circuit is implemented in variable gain amplifier. Based on the output of piezoelectric microphone, designed gain control circuit automatically sets the gain. The investigated analog front end offers lower noise and wider dynamic range with compact size compared to conventional architecture. It achieves a 42 $$\mathrm{n}V_{rms}$$ input referred noise and 84 dB signal to noise ratio. The total area of the designed analog front end circuit is 386 $$\upmu \mathrm{m}$$ $$\times$$ 569 $$\upmu \mathrm{m}$$ . Designed circuit is interfaced with a sensor model of piezoelectric microphone and its performance is successfully verified against simulation results.