be proportional to the current flowing through the electrode 30 as explained to some extent above while the embodiments illustrated in fig4 a and 5 employ two switches 34 and 36 connected in series to control the loading of the capacitor 32 one switch being controlled by each of the row and column lines respectively those skilled in the art will appreciate that the switching function may be implemented in any of a number of ways for example it would be considered equivalent to replace the switches 34 and 36 shown in fig4 a and 5 with cmos transmission gates or a combination of an and gate and a switch turning again to fig4 c in a preferred form the biologic array 10 may be fabricated using a cmos or other active circuit process moreover those skilled in the art will appreciate that completely fabricated cmos circuitry embodying some or all of the above described functions may be post processed to form the complete active biologic electrode array 10 described above for example as illustrated in fig6 the biologic electrodes 30 may be disposed atop the underlying cmos circuitry and then protected with an overlapping passivation layer 44 further openings in the passivation layer 44 may be fabricated to expose the active regions of the biologic electrodes 30 as well as any required peripheral interconnection sites e g bond pads not shown in such an embodiment the electrodes 30 may be fabricated from electrochemically suitable materials such as gold iridium or platinum and may be deposited and patterned using conventional thin film deposition techniques the passivation layer 44 may comprise for example plasma deposited silicon nitride and or silicon carbide and openings in the passivation layer 44.