Abstract
The use of dry electrodes is increasing rapidly. Since their impedance is high, there is a high impedance node at the connecting node between the electrode and amplifier. This leads to absorb powerline signal and high CMRR amplifiers are essential to eliminate this. In this article, we propose a low-power low-noise chopper-stabilized amplifier with high CMRR. In order to minimise the input-referred noise, an inverter-based differential amplifier is utilized. Meanwhile, a DC servo loop is designed to reject the DC offset of the electrode. Since all of the stages required a common-mode feedback, for each of the amplifiers a suitable circuit was used. Furthermore, a chopping spike filter is implemented at the final stage to attenuate the choppers’ spike. Finally, to eliminate the offset effect from the mismatch and post-layout, a DC offset rejection technique is used. The designed circuit is simulated in a standard 180 nm CMOS technology. The designed chopper amplifier consumes just 1.1 upmu hbox {W} at a 1.2 hbox {V} supply. The mid-band gain is 40 dB while the bandwidth is from 0.5 to 200 Hz. The total input-referred noise is 1 upmu hbox {V}_{mathrm{rms}} in its bandwidth. Thus the NEF and PEF of the designed circuit is 2.7 and 9.7, respectively. In order to analyse the performance of the proposed chopper amplifier against process and mismatch variation, Monte Carlo simulation is done. According to 200 Monte Carlo simulations, CMRR and PSRR are 124 dB with 6.9 dB standard deviation and 107 dB with 7.7 standard deviation, respectively. Ultimately, the total area consumption is 0.1 hbox {mm}^2 without pads.
Highlights
The importance of EEG signals is growing rapidly in the decades, owing to their high potential for use in the early diagnosis of ailments
We propose a low-power low-noise chopper-stabilized amplifier with high CMRR
We have focused on a low-power and high CMRR amplifier in order to minimise the capacitive and inductive picked up noise to achieve a higher SNR in EEG systems
Summary
The importance of EEG signals is growing rapidly in the decades, owing to their high potential for use in the early diagnosis of ailments. Dry electrodes are more suitable for prolonged use than wet electrodes, they have a higher skin to electrode impedance and a lower signal to noise ratio. In order to overcome this problem, a high CMRR biomedical amplifier could offer a solution due to the fact that the 50/60 Hz noise is like a common-mode signal in all of the electrodes. In this case, we are able to overcome some of the obstacles when moving towards dry electrodes, which. Chopper amplifiers usually use a high switching frequency to minimise the flicker noise of a circuit Their input impedance is lower than other techniques. A high CMRR biomedical amplifier is essential for the future of dry electrodes
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