Design of a fast voltage clamp for biological membranes, using discontinuous feedback

Abstract

The construction of a voltage clamp with discontinuous feedback is described. Its main feature is a pulsed membrane current with an amplitude proportional to the voltage error, which is determined by integration in the pulse intervals. A current pulse of 8 μsec length repeating every 24 μsec is used. Gain switching assures a fast response to large errors, as well as high steady state accuracy. Membrane voltage changes by 150 mV in 8 μsec to 1% of the final value. 50 μsec after such a step, a change of resistive membrane current can be read reliably. Performance is demonstrated with equivalent networks of biological membranes and with applications to black lipid membranes and epithelial membranes.