5.3 A 2-channel −83.2dB crosstalk 0.061mm<sup>2</sup> CCIA with an orthogonal frequency chopping technique

Abstract

Area-efficient low-noise instrumentation amplifiers (IAs) are required in various multi-channel sensing and monitoring applications. These IAs must be designed to achieve low noise and low power, good noise efficiency factor (NEF), good gain matching and low crosstalk among multiple channels [1]. For a continuous sensor array application, each sensor unit is conventionally connected to an individual amplifier for analog signal processing. This configuration consumes large chip area and high power. Furthermore, the quality of gain matching among channels is limited due to the independence of each channel. In [2-3], several multi-channel schemes addressing some of these difficulties are reported. This paper demonstrates a prototype capacitively-coupled IA (CCIA) that adopts an orthogonal frequency chopping (OFC) technique to realize a continuous two-channel CCIA with only one active amplifier, thus saving chip area and power. The whole two-channel CCIA, realized in 0.35μm CMOS, occupies an active area of 0.061mm2 (area per channel is 0.0305mm2). This 2-channel IA draws 27μA from a 3V supply. It achieves a low input-referred noise of 26nVA/Hz, reasonable NEF of 3.74, and good gain matching with mismatch of less than 0.55%. The average crosstalk between two channels is −83.2dB, which is about 10dB better than those reported in designs of similar framework [2-3].