Wide dynamic range front-end amplifier for cell recording with microelectrode arrays

Abstract

In a cell recording system, characteristics of the cell and microelectrode array (MEA) interface impose challenging requirements on the design of front-end amplifier with regard to input-referred noise, linearity, dynamic range (DR), input impedance, pitch size and differential electrode offset (DEO) cancellation. Previous front-end amplifier designs for cell recording demonstrated 2~7 ¿V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</sub> input referred noise and about 1% total harmonic distortion (THD) for dozens of mV <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pp</sub> input signal, which corresponds to about 60 dB DR. However, front-end with wider DR is needed for many new cellular applications. This paper reports the design of a new wide DR front-end amplifier which uses chopping to suppress the noise, and a new current feedback scheme to improve the linearity. The new design is implemented in a 0.35 ¿m CMOS process. SPICE simulation shows that the new amplifier achieves THD lower than -70 dB with 20 mV <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pp</sub> input signal and 0.75 ¿V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</sub> input-referred noise. For local field potentials (<200 Hz), the DR extends to 80 dB. The new amplifier has more than 0.62G ¿ input impedance at 20 kHz and consumes 20 ¿W power.