I am trying to make a fast switching circuit that is able to switch a current (0-20mA) supplied by a current source (open-circuit voltage 100V) between two channels (i.e. switching between two pairs of electrodes). The load has a low resistance (100-250 ohhm). The current signal is composed of square pulses of (5-20ms) duration, one pulse every 300ms.
I have a CD4067BE 1x16 multiplexer operated at 15v/0v Vdd/Vss to minimize its on-state resistance. At 15v, channel selecting voltage should be at min. 11v for logic 1.
my questions:
How to limit the input voltage coming from the current source to MUX such it does not exceed 15v? can I use zener diode without any harm to the current source?
I am using MCU signals (0-5v) to control selection inputs of the MUX. However, at least 11v is needed to activate selection. What a driving circuit do you suggest?