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.
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?