Hysteretic switching

One last form of voltage-mode eontrol is very rudimentary. It eould be ealled hysteretic voltage-mode. In this form of eontrol, a fixed frequency oscillator is gated ON only when the output voltage has fallen to below a limit dictated by the voltage feedback loop. It is sometimes called hiccup-mode because the power switch occasionally bursts on and then returns to a constant off state. 

During the past 20 years, mechanically interlocked molecules, known as catenanes and rotaxanes, many of them redox-active, have become readily accessible using template-directed protocols that rely upon the precepts of molecular recognition and self-assembly and the tenets of supramolecular assistance to covalent synthesis. By incorporating different recognition units with dissimilar redox properties into appropriate components, these compounds can often be induced to switch hysteretically between ground and metastable co-con-... 

Figure 4. Effect of epitaxial (or deposition) strains on the average extrinsic ferroelectric behavior of a polycrystalline thin-film [83], Left inset summarizes the predicted out-of-plane hysteretic response, while the right inset embodies the predicted out-of-plane extrinsic electromechanical behavior. Note that while the electromechanical response for large fields corresponds to the equilibrium (intrinsic) behavior, a great potential for reaching electromechanical enhancements up to one order of magnitude greater than the ones currently available are possible by harnessing the time-dependent switching behavior.

FIGURE 4 The hysteretic response (top) and switch cycling (bottom) of a molecular-electronic switch consisting of a bistable [2]rotaxane sandwiched between a polysilicon bottom electrode and a Ti/Al top electrode. The device dimensions are approximately 50 X 50 nm. Control data from the dumbbell component (the [2]rotaxane without the TCP4+ ring) are included. 

Rudquist, P. D. Krilerke, J. E. LagerwaU, J. E. Macleiman, N. A. Clark, andD. M. Walba. 2000. The hysteretic behavior of V-shaped switching smectic materials. Fermelectrics. 

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