For ISFET-based sensors, low-frequency noise is most detrimental to the overall SNR as it can interfere with biomedical signals which span in the same frequency domain. The noise has mainly three sources. The noise sources outside the ISFET itself are referred to as the external noise, such as environmental interference and instrument noise from terminal read-out circuits. The intrinsic noise refers to that appearing in the solid part of an ISFET, which is mainly caused by the trapping and de-trapping of carriers at the Oxide/Si interface. And the extrinsic noise is generally rooted in the liquid/oxide interface causing by the ion exchange at the liquid/oxide interface. Many methods are invented to suppress the noise of ISFET. For example, to suppress the external noise, we can integrate a bipolar junction transistor with ISFET to realize immediate the internal amplification of drain current. And to suppress the intrinsic noise we can replace the noisy oxide/Si interface by a Schottky junction gate.