A low power sensor signal processing circuit for implantable biosensor applications

A low power sensor read-out circuit has been implemented in 0.35 mu m CMOS technology that consumes only 400 mu W of power and occupies an area of 0.66 mm(2). The circuit is capable of converting the current signal from any generic biosensor into an amplitude shift keying ( ASK) signal. The on-chip potentiostat biases the chemical sensor electrodes to create the sensor current which is then integrated and buffered to generate a square wave with a frequency proportional to the sensor current level. A programmable frequency divider is incorporated to fix the ASK envelope frequency to be inbetween 20 Hz and 20 kHz, which is within the audible range of human hearing. The entire transmitter block operates with a supply voltage as low as 1.5 V, and it can be easily powered up by an external RF source. Test results emulate the simulation results with good agreement and corroborate the efficacy of the designed system.