Electrochemical digital circuits

The inverter requires a symmetrical +/— 3 V supply. It is possible to lower the supply voltage to +/ — 2 V at the cost of one more transistor by exchanging the resistor R for a current generator as shown in Fig. 9.9. 

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The field of cathode activation, as well as that of anode activation, requires the use of complementary physical techniques to evaluate systems otherwise difficult to understand. Electrochemical techniques are sufficient to evaluate the kinetic parameters and the state of intermediates, especially if digital acquisition of open-circuit potential-decay transients, coupled with computer processing of the data, is used [104-106]. But the chemical and physical characterization of the surface remains essential. The literature shows that such an approach is becoming more accepted, so that there are hopes that the real situation of a number of systems will become clarified in the near future. 

The electrochemical timer is a device that can be set to switch a circuit on or off at a given time. It was of great practical importance until the development of microelectronic digital devices, since it could be set to operate for periods of minutes to months, with an accuracy of better than 1%. We describe it here to show how an understanding of the fundamental electrochemical processes taking place can lead to the development of a simple and very useful device. 

SPICE [32] simulations indicate that the electrochemical transistor can be used favorably to implement a number of useful digital and analogue circuits. Naturally, the slower speed, compared to traditional electronics (by about a factor 108 ), should be taken into consideration. The area of (silicon-based) electronic circuit theory offers numerous solutions to the implementations of circuits. However, depletion-type transistors are less favorable to use in system designs than their enhancement counterparts. For this reason, it is rare to find circuits that use depletion transistors. One has to go back to the electron tube era to find solutions that can be used as templates for circuits suitable for the electrochemical transistor. 

D. Laser and A. J. Bard, Semiconductor electrodes VIII. Digital simulation of open-circuit photopotentials, J. Electrochem. Soc. 123 (1976) 1833-1837. 

Figure 3 shows a schematic of the FIA system and details the thin-layer transducer cell, which contains the poly(3-methylthiophene) anion sensor electrode(s). Electrochemical detection in the amperometric mode was employed for the FIA/EC (flow injection analysis with electrochemical detection) studies. A typical potential used was +1.00 volts vs. Ag/AgCl reference electrode. The FIA-EC system consisted of an Altex lOOA double reciprocation pump and a Rheodyne injector (Cotai, CA) with either a 20 or 50 microliter sample loop. Constant potentials were applied using the herein described DWEP, which is software controlled. The electronically transduced signals are converted from analog to digital by use of A/D and D/A converter circuits. The option exists to automatically save the data on the computer or print the results as the experiment progresses. 

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