The use of control theory for the design of voltage clamp systems: a simple and standardized procedure for evaluating system parameters

Voltage clamp (VC) instruments are closed-loop control systems based on ele ctronic feedback. Such feedback systems can be described in the framework o f control theory. We used a mathematical approach based on control theory t o improve the performance of VC systems. This approach considerably simplif ies the design and optimal tuning of these systems, as is demonstrated for a standard two electrode and a time-sharing single electrode clamp system. The major advantage of this approach and the consequent optimization proced ure is that only proportional-integral controllers for VC systems must be u sed. As a consequence, the design of such VC systems is solely based on the time constants of the clamp circuit. In our approach, the 'symmetrical opt imum' rule was applied for the first time to VC systems. This yields optimi zed systems with respect to speed of response and clamp accuracy. An empiri cal procedure has been derived from this theoretical approach which allows the optimal tuning of VC instruments based on PI controllers while running an experiment. (C) 2001 Elsevier Science B.V. All rights reserved.