Rear Panel
Expansion Slots
There are three expansion slots along the top of the rear panel. One of these is occupied by the headstage driver electronics, and the other two are general-purpose. They are intended for future optional accessories such as the 8-pole Bessel filter upgrade.
The reason for putting the headstage driver electronics on a separate board
is to allow the basic Optopatch design to accommodate other types of headstage
for different applications, e.g. a standard resistive feedback design for
higher current ranges. It also facilitates calibration adjustments, as the four
pre-sets on the driver circuit board (described in more detail elsewhere) are
directly accessible from the rear panel. The adjustments are for headstage
voltage offset, optical bias, and bandwidth in the patch and (big) cell current
ranges. These pre-sets should be adjusted to match the headstage in use, while
calibrating the four optical sensitivity pre-sets on the headstage at the same
time. The driver subpanel also has switches for selecting the full-scale
current in the small cell voltage and current clamp modes (1nA or 100nA), and
for the Peltier cooler in the headstage. In addition, there is a 9-pin D
connector, which provides a variety of outputs that are useful for calibration.
One of these (pin 2, with ground on pins 6 and 7) is a direct equalised signal
output from the current-to-voltage converter circuit, which we recommend for
any applications that exploit the unusually high bandwidth of this system.
