A General Purpose Amplifier Design for Low-Frequency Weak Signal Acquisition

A general purpose amplifier for low-frequency weak signal acquisition fabricated in CSMC 0.5μm 2P3M process is presented. The amplifier adopts full differential structure with AC-coupled and capacitive feedback, the input resistor is boosted and bandwidth can be adjusted. The amplifier uses PMOS pseudo resistor to realize the adjustment of high pass cutoff frequency through adjusting gate voltage, which suits different low-frequency weak signal acquisition. The tested gain of the amplifier is 45.2dB. The high pass cutoff frequency can be adjusted from 1Hz to 10kHz. The equivalent input-referred noise within 100Hz and 7kHz is 17.8μV.