Sub-threshold Current Conveyer for Current-Mode Processing Bio-Analog Front Ends

Current-mode analog front ends for reading biosensors have emerged as a prominent design approach in recent times. This method involves processing input current signals directly with current-mode blocks instead of converting them to voltage and utilizing voltage-mode blocks. The primary advantages include reduced power consumption, minimized area usage, and increased dynamic range, particularly at low voltage levels. In current-mode design, the current conveyor plays a pivotal role. Therefore, this work focuses on the design and fabrication of a second generation current conveyor (CCII) to serve as a current buffer in low-LED photoplethysmography (PPG) or any bio-potential readout analog front end with input currents ranging from 1.5nA to 1000nA. Our fabricated CCII consumes 1.79µW and the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\beta$</tex> dependency to the load is improved 33% in compared to previous design. Also, X node follows Y node voltage with 10mv variation for full input current range. The area usage of our CCII is <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$3400 um^{2}$</tex>.