555 as a MOSFET Driver

As outlined in the Mr.T's Design Graveyard video below, to effectively drive a standard MOSFET, you need to provide around 12V, along with enough current to charge its gate fast enough. Arduinos – and other similar dev boards – typically source either 3.3V or 5V, with a limited amount of current.

Therefore, if you want to switch a standard MOSFET with an Arduino you’ll need an intermediary (e.g. a driver) to do the heavy 12V lifting in your circuit. While you might not have a dedicated MOSFET driver lying around, you may instead have a 555 chip, like the NE555, available, which can be used to build a simple MOSFET driver.

Mr.T’s circuit pulls the 555 threshold pin to 12V and its trigger to ground, making the output pin high by default. The reset pin is connected to the Arduino PWM output–pin D2 of an Arduino Nano is shown, but other pins should work. The 555 output goes high when the (Arduino) input is over .7V, and low when it goes below that threshold.

The 555/Arduino circuit results are shown on an oscilloscope at around the 3:00 mark in the video, using an Arduino to trigger the 555, which in turn switches a MOSFET that controls a 24VDC output. There is some switching delay between the two components, which becomes more noticeable as the frequency is increased. So while using a 555 timer as a MOSFET driver is a useful tool, as with any component you’ll need to analyze its performance in the context of your particular circuit.

Notably, some MOSFETs are designated as logic-level devices and can be driven directly by an Arduino or similar. Otherwise one might say, “Just use a 555!”