Preparing Input and Selection voltages to a Multiplexer
... to switch a current (0-20mA) supplied by a current source (open-circuit voltage 100 V ... The load has a low resistance (100-250 ohm). The current signal is composed of square pulses of (5 - 20ms) duration, one pulse every 300ms.


20 mA into 250 Ω means that maximum load voltage will be \$ V = 20m \times 250 = 5~V \$. This makes it unclear why you need a 100 V source voltage. I suspect that it is because that's the voltage you will need to strike or spark on the electrode.

In any case, at 100 V this chip is not the solution to your problem. You could use a Zener diode to limit the voltage but your electrodes may not work at the low voltage.







simulate this circuit &ndash; Schematic created using CircuitLab

Figure 1. An alternative control strategy.

You could consider digital switching of the source using a suitably high-voltage transistor driven by an opto-isolators which in turn are controlled by your micro.