Amplifiers for biological signals aimed to implantable medical devices require high gain and low noise, while maintaining very low power consumption. Therefore, a major challenge is the design of efficient low-noise circuits. These amplifiers work at low frequency ranging from sub-Hz to few kHz, thus besides the presence of thermal (white) noise, flicker noise (1/f noise) can be the largest. Autozero technique is used to reduce offset and flicker noise. However, a main issue in this kind of amplifiers is the aliasing of white noise inherit to the switching process, which increases the noise floor at low frequencies. In this work, the design of a low-noise amplifier for electroencephalography (EEG) signal recording is presented. The Autozero technique is applied to an instrumentation amplifier in the range of biological signals, with the addition of a low-pass filter in the noise cancellation feedback with the objective of reducing the impact of aliasing. Time domain simulations of the proposed amplifier show the benefits of the used architecture.
['Guillermo Costa', 'Alfredo Arnaud', 'Matías R. Miguez']
A precision autozero amplifier for EEG signals