Introduction to Electrochemical Circuits and Systems

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. 

A closer investigation of the possible modes of operation given by the transistor characteristics shown in Fig. 9.1 reveals that the third-quadrant mode is superior to the first-quadrant mode. It is not possible to achieve amplification at all in the first quadrant while this is easy to achieve in the third quadrant. Thus, circuit designs should utilize the transistor in the third-quadrant mode. However, the range of the input and output voltages do not overlap, which introduces some added complexity in system designs. 

In the design of circuits there are certain basic electrical design rules for the electrochemical transistor that should be kept in mind  

The third rule can be made more specific The gate potential should never become more negative than the most negative potential in the channel of the transistor. Usually the most negative potential is the drain potential but it is possible (if the gate voltage falls rapidly), that part of the channel may overoxidize due to dynamic effects. A more conservative rule that is always safe is to avoid decreases of the gate potential below the source potential. 

The organic-based OECT, reported here, can handle remarkably higher power than its OFET relatives. As an example, an Orgacon (particular grade of PEDOT PSS from AGFA)-based transistor with active channel size 0.5 x 0.5 mm2 can handle a switching power of up to 20 mW. Above this power level breakdown occurs, most likely due to thermal stress. The transistor can also handle voltages of up to 70 V as well as currents up to 1 mA. 

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