A low power and ultra-high input impedance analog front end based on fully differential difference inverter-based amplifier for biomedical applications

In this paper, a low power and low noise analog front end (AFE) is designed for biosignal acquisition. The first stage is a low noise amplifier (LNA) that is designed by combining the fully differential difference amplifier (FDDA) structure with inverter-based to achieve the optimal power, noise, CMRR, and input impedance simultaneously. Also, to increase the output resistance of the LNA, and subsequently increase the gain without reducing the output voltage swing, the gain boosting technique has been used. To use this structure for biosignals, the second stage is designed as a programmable gain amplifier (PGA). This AFE is reconfigurable for electroencephalography (EEG), electrocardiogram (ECG), and surface electromyography (sEMG) biosignals with variable gain of 71 dB, 56 dB, and 44 dB and bandwidth of (0.9-100 Hz), (1-560 Hz) and (12 Hz-1.5 kHz), respectively. The AFE consumes only 303 nW at 0.8 V supply voltage and confers excellent input impedance of 250 G Omega and 5.2 G Omega when the chopper is "off' and "on" respectively. The chopper method has been used and the total integrated input-referred noise is obtained, 1.4 mu V-rms. The proposed AFE is simulated in TSMC 65 nm CMOS technology and occupies an area of 0.16mm(2).