Current Mode: Bipolar Stimulation configuration and Maximum Amplitude?

I've setup our STG2004 to generate biphasic lilly pulses, in current mode, ranging from 0.125mA to 3.0mA. When measuring and visualizing the voltage waveforms on an oscilloscope, and using a 10KOhm load (our electrode loads typically range from 4KOhm to 12KOhm), as illustrated on page 68 in the +1 to -1 configuration, the pulse amplitude and shape are solid as expected, yet in the instruction manual on page 64, 11.3 Current Mode, the "maximum output current in current mode is only 0.8mA." Am I missing something here?

Second, when in current mode: bipolar stimulation (page 67 of the manual), current is "not" actually flowing from electrode 1 to electrode 2, as in a source and sink configuration, but a potential is setup within the tissue, based on the opposite polarities of the single pulse being passed through +1 and -1 outputs, correct? In voltage mode: bipolar stimulation this is not the case, current is actually flowing between the electrode 1 and electrode 2, correct?

Dear jbozoman,

we provide various configurations of STGs with different maximum current outputs.
If you e-mail us the serial number of your device I will be glad to look up the specs for your STG.

In Current mode the compliance voltage will drive the current defined in the software.

The figure illustrates that you can use the +I and -I outputs to get an inverted pulse from the -I output.

Current will flow through the designated output and charge is delivered to the respective MEA electrode, however in no configuration (current or voltage) current will neccessarily flow between the two designated stimulation electrode.

Thomas

The figure illustrates that you can use the +I and -I outputs to get an inverted pulse from the -I output.

Current will flow through the designated output and charge is delivered to the respective MEA electrode, however in no configuration (current or voltage) current will neccessarily flow between the two designated stimulation electrode.

To clarify, in Current Mode: bipolar stimulation, the current flow is independently delivered to the +1 and -1 outputs and the return path for the current delivered is the common ground (shield) illustrated in the figure on page 67.
Therefore, in order to pass current between two electrodes, one must setup the stimulation in Current Mode: Standard Setup and designate one electrode as ground, attached to the GND output and the other electrode connected to the +1 output?

Hi Jonathan,

you are correct here (for the first section), for details, please also see my reply to your e-mail.

Even if you have two current outputs against ground you will just have a field between the electrodes.
Not neccesarily the defined current completely flowing from one electrode to another.

Thomas