I'm trying to use a p-channel MOSFET (FQP27P06) to multiplex four large common-anode seven-segment displays. I'm using a TPIC6B595 high voltage high current shift register to sink the segments for each digit.
I'd like to use the MOSFET to multiplex and control brightness of the four digits by giving the common anode 18 V.
Here is a simple schematic for driving the MOSFET. My concern is when the MOSFET is 'open' I'm seeing the 18 V on the pin which would be hooked up to the microcontroller.
Is the NPN transistor even necessary?
The second schematic has an extra resistor forming a voltage divider to limit the voltage going to the gate of the MOSFET. I don't think it is necessary with this MOSFET.
I have put the circuit together on a breadboard, but I am hesitant to hook it up to the Arduino.