IR2125 mosfet driver quickstart guide

IR2125 Mosfet driver in a circuit

IR2125 mosfet driver

The IR2125 driver is a simpler IC than the IR2110 dual channel high side low side driver. If you only need to switch a single high side mosfet than this is your IC of choice even though it is a bit more expensive because of it’s lesser popularity.

Capabilities of the IR2125 gate driver

  • The IR2125 comes in both DIP8 and SOIC16 packages.
  •  A single channel capable of bootstrapping a floating mosfet. High side and  low side switching are possible.
  • Mosfet drain can get up to 500V. This is your maximum switching voltage.
  • Mosfet gate voltage  must be between 12 and 18. Do consider this when selecting a mosfet.
  • Can understand 3.3V, 5V and 15V logic. Can connect directly to your Arduino, Atmel or PIC.
  • Switching times are as low as 150ns. This gives a theoretical maximum switching frequency of 6.6Mhz.

Gate driver typical circuit

The IR2125 needs three capacitors and a diode to function. Also, a resistor to the gate of the mosfet is recommended.

IR2125 Mosfet driver in a circuit
IR2125 mosfet driver circuit application


Pin functions of the driver IC


The VCC pin receives power to feed the driver IC and to switch the gate of the mosfet. Make sure it is at least 10V. It is also connected to VB through a diode to charge the bootstrap capacitor when needed. A smoothing capacitor is added to keep a stable voltage supply for the IC.


Signal from your controller is fed into this pin. Anything above 2.2V is considered a high signal.


This pin is not used by mere mortals. Attach a capacitor to keep the pin from floating.


Ground reference for the IC. Simply connect it to the ground of your controller.


The VB pin connects to a bootstrap capacitor which stores energy to switch the mosfet. When the source of the mosfet drops to ground (when the mosfet is off), the bootstrap capacitor gets charged through the diode.


When the mosfet is switched on, the bootstrap capacitor on the VB pin is connected to HO pin, switching the mosfet on.


Is a current detector pin to connect to the same pin on the mosfet. Not needed for normal usage. Just keep it disconnected.


Source line of the mosfet. Needed keep the gate capacitor on VB floated at same level as the mosfet.


I think the IR2125 gate driver IC is somewhat simpler to set up compared to the IR2110. If money is not an issue, then I suggest using the IR2125.