Implantable biosensor

An apparatus, comprising:

• an electrochemical cell comprising a reference electrode, a control electrode, a first working electrode, a second working electrode, and a third working electrode, the electrochemical cell configured to perform a plurality of electrochemical measurements, the plurality of electrochemical measurements including a first measurement of an analyte concentration in a body fluid, the first measurement corresponding to a first current flow between the first working electrode and the control electrode, a second measurement of a background interference present in the body fluid, the second measurement corresponding to a second current flow between the second working electrode and the control electrode, and a third measurement of a pH level within the body fluid, and the third measurement corresponding to a voltage difference between the third working electrode and the reference electrode;
• a potentiostat coupled with the electrochemical cell, the potentiostat comprising at least a first current control loop configured to limit the first current flow between the first working electrode and the control electrode to a maximum current so as to reduce power consumption, wherein the maximum current is determined by a range of physiological levels of the analyte concentration present in the body fluid;
• a current-starved diode connected differential transconductance amplifier configured with an overall transconductance to match a physiological pH level range present in the body fluid;
• and
• an antenna configured to respond to one or more radio frequency waves output by a transceiver by at least transmitting, to the transceiver, a backscatter signal encoding a result of the plurality of electrochemical measurements, the backscatter signal exhibiting a cyclical pattern generated by selecting between the first current flow, the second current flow, and the voltage difference, the cyclical pattern including comprising a first quantity of cycles that correspond to the pH level, a second quantity of cycles that correspond to the analyte concentration, and a third quantity of cycles that correspond to the background interference, the apparatus being wirelessly powered by the one or more radio frequency waves instead of an onboard power source in order to minimize a first size of the apparatus, the one or more radio frequency waves having a high frequency such that the first size of the apparatus is further minimized by minimizing a second size of the antenna.