A low noise CMOS instrumentation amplifier for integrated thermal gas flow sensor

A low noise CMOS instrumentation amplifier is realized to meet the requirements of an integrated thermal gas flow sensor for very weak and low frequency signal amplification. To avoid the offset and 1/f noise introduced by CMOS processes, a chopper stabilized technique is used to modulate the wanted signal to a higher frequency while keeping the distortion in the lower band. Simulation results have shown that the gain of the amplifier is about 500, and the equivalent input offset is no more than 1 μV and the equivalent input noise PSD is 36 nV/√(Hz). The sensor can measure wind speed of 0 to 23 m/s and is 360° sensitive.