Differential reference input
The Optopatch headstage incorporates a high-impedance differential input in the headstage. We have provided this facility this because of the grounding problems that arise when two or more patch clamps (of any make) are used together. The difficulty is that when the bath electrode is properly grounded as far as one patch clamp is concerned, the other patch clamps see a signal here (mainly at the power line frequency and its harmonics), because their grounds are actually all at slightly different potentials. The Optopatch can now get around this problem by measuring signals differentially with respect to the bath potential, so the bath can now be taken to whatever ground connection is most convenient for other reasons (note that it still needs to be grounded to something!).
If differential operation is not required,
it can be disabled by moving the appropriately labelled jumper link on the
headstage driver board. However, whenever the differential input is not in
use, whether or not it has been disabled, we recommend that it is connected
to the ground pin on the headstage using the connector lead supplied for the
purpose.
