--_____ TA 9.5: An Integrated CMOS Potentiostat for Miniaturized Electroanalytical Instrumentation

Two major limiting factors in mass production and field use of electroanalytical instruments have been the size and cost of potentiostats [ l, 21. This monolithic CMOS potentiostat has performance comparable to bench-top instruments at a frac-tion of the size, power consumption and cost. Figure 1 shows the block diagram of the potentiostat chip. An integrating DAC sets the voltage between the working electrode, where the electrochemical reactions of interest take place, and a chemically stable reference electrode. The control amplifier regulates this voltage using feedback to drive a third (counter) electrode. The working electrode current is measured with a current-input dual-slope ADC. Precision switchedcapacitor techniques are used throughout to cancel voltage offsets and minimize charge-injection errors. Representative of these techniques is the control amplifier