A Variable Gain and Bandwidth Fully Differential CMOS Neural Preamplifier

The design of a low noise low power fully-differential CMOS preamplifier for bioelectrical signals recording applications is presented. The capacitive-coupled and capacitive-feedback topology is adopted. The amplifier current consumption is $5.2\ \mu \mathrm{A}$ or $18.2\ \mu \mathrm{A}$ at 3 V supply for a mid-band gain of 39.4 dB or 25.9 dB, respectively. Each corner frequency is 2-bit programmable for amplifying biosignals located in different bands. The bandwidth can be extend from 0.15 Hz - 2.68 kHz to 0.03 Hz - 40.4 kHz. To avoid possible saturation at the differential output, a discharged switch is incorporated. The circuit has an input-referred noise of $2.99\ \mu \text{Vrms}$ integrated from 0.1 Hz to 10 kHz. It was designed and simulated using $0.5\ \mu \mathrm{m}$ 3M2P CMOS process. The circuit is in the manufacturing process.