Clamping circuit

Record response to applied ligand with voltage clamp circuit... 

Figure 7.25 shows a similar three-electrode voltage intracellular clamp circuit. A problem with the circuits is that two micro-electrodes must be introduced through file cell membrane. 

Figure 7.25 Intracellular three-electrode voltage clamp circuits, (a) ellipsoid cell form, (b) nerve...

Figure 8.19 Three noise reduction approaches. Left grounded patient. Middle floating patient with instrumentational amplifier. Right ground-clamping circuit. Vp is typical patient AC voltage with respect to ground. Vp is in practice nonsinusoidal. Because of the high-pass filtering effects, the harmonics of the mains supply are expanded.

The voltage-clamp technique was introduced by Cole in 1949. A general survey of the principle of operation and various shortcomings is presented by Moore and Cole (1963). A voltage-clamp circuit provides a means for holding constant the potential difference across the resting or active plasma membrane of a neuron (axon), within the limitations of practical electrodes. The discussion here is concerned primarily with the amplifier system being used. 

Figure 7.32 illustrates the basic clamp circuit. A differential amplifier is used. The mathematical relations which describe voltage-clamp operation are... 

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