| 摘要 |
A precision circuit for measuring electrical currents, of the order of only a few pico-amperes, in the individual ionic channels of biological membranes, comprising a pipette engaging a membrane and having an internal electrode connected to a current-to-voltage converter; the converter output is integrated and fed back to a reference potential source for the converter to control that reference potential so that the average pipette electrode is maintained at zero over a predetermined time interval. In the preferred construction the time constant of the feedback integrator is adjustable between a "slow" value and a "fast" value; at the "slow" setting the long-term average of the pipette current is forced to be zero, whereas at the "fast" setting it is possible to measure the potential at the pipette tip at zero current.
|
